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30DaysOfPython

🧳 Part 1: Day 1 - 3
🧳 Part 2: Day 4 - 6
🧳 Part 3: Day 7 - 9
🧳 Part 4: Day 10 - 12
🧳 Part 5: Day 13 - 15
🧳 Part 6: Day 16 - 18
🧳 Part 7: Day 19 - 21
🧳 Part 8: Day 22 - 24
🧳 Part 9: Day 25 - 27
🧳 Part 10: Day 28 - 30

Day 4

String

Text is a string data type. Any data type written as text is a string. Any data under single or double quote are strings. There are different string methods and built-in functions to deal with string data types. To check the length of a string use the len() method.

Creating a string

letter = 'P'                # A string could be a single character or a bunch of texts
print(letter)               # P
print(len(letter))          # 1
greeting = 'Hello, World!'  # String could be  a single or double quote,"Hello, World!"
print(greeting)             # Hello, World!
print(len(greeting))        # 13
sentence = "I hope you are enjoying 30 days of python challenge"
print(sentence)

Multiline string is created by using triple ''' or quotes.See the example below.

multiline_string = '''I am a teacher and enjoy teaching.
I didn't find anything as rewarding as empowering people.
That is why I created 30 days of python.'''
print(multiline_string)
# Another way of doing the same thing
multiline_string = """I am a teacher and enjoy teaching.
I didn't find anything as rewarding as empowering people.
That is why I created 30 days of python."""
print(multiline_string)

String Concatenation

We can connect to strings together. Merging or connecting to strings together is called concatenation.See the example below

first_name = 'Asabeneh'
last_name = 'Yetayeh'
space = ' '
full_name = first_name  +  space + last_name
print(full_name) # Asabeneh Yetayeh
# Checking length of a string using len() builtin function
print(len(first_name))  # 8
print(len(last_name))   # 7
print(len(first_name) > len(last_name)) # True
print(len(full_name)) # 15

Escape Sequences in string

In python and other programming language followed by a character. Let's see the most common escape characters:

  • \n: new line
  • \t: Tab means(8 spaces)
  • \\: Back slash
  • \': Single quote (')
  • \":Double quote (")
print('I hope every one enjoying the python challenge.\nDo you ?') # line break
print('Days\tTopics\tExercises')
print('Day 1\t3\t5')
print('Day 2\t3\t5')
print('Day 3\t3\t5')
print('Day 4\t3\t5')
print('This is a back slash  symbol (\\)') # To write a back slash
print('In every programming language it starts with \"Hello, World!\"') 

# output
I hope every one enjoying the python challenge.
Do you ?
Days    Topics  Exercises
Day 1   5       5
Day 2   6       20
Day 3   5       23
Day 4   1       35
This is a back slash  symbol (\)
In every programming language it starts with "Hello, World!"

String formating

Old Style String Formatting (% Operator)

In python there many ways of formating string. In this section we will cover some of them. The "%" operator is used to format a set of variables enclosed in a "tuple" (a fixed size list), together with a format string, which contains normal text together with "argument specifiers", special symbols like "%s", "%d", "%f", "%.f".

  • %s - String (or any object with a string representation, like numbers)
  • %d - Integers
  • %f - Floating point numbers
  • %.f - Floating point numbers with a fixed amount of digits to the right of the dot.
# Strings only
first_name = 'Asabeneh'
last_name = 'Yetayeh'
language = 'Python'
formatted_string = 'I am %s %s. I teach %s' %(first_name, last_name, language)
print(formatted_string)

# Strings  and numbers
radius = 10
pi = 3.14
area = pi * radius ** 2
formatted_string = 'The area of radius %d is %.2f.' %(radius, area) # 2 refers the 2 significant digits after the point

python_libraries = ['Django', 'Flask', 'Numpy', 'Pandas']
formatted_string = 'The following are python libraries:' % python_libraries
print(formatted_string) # "The following are python libraries:['Django', 'Flask', 'Numpy', 'Pandas']"

New Style String Formatting (str.format)

This is formating is introduced in python version 3. 

first_name = 'Asabeneh'
last_name = 'Yetayeh'
language = 'Python'
formatted_string = 'I am {} {}. I teach {}'.format(first_name, last_name, language)
print(formatted_string)
a = 4
b = 3

print('{} + {} = {}'.format(a, b, a + b))
print('{} - {} = {}'.format(a, b, a - b))
print('{} * {} = {}'.format(a, b, a * b))
print('{} / {} = {:.2f}'.format(a, b, a / b)) # limits it to two digits after decimal
print('{} % {} = {}'.format(a, b, a % b))
print('{} // {} = {}'.format(a, b, a // b))
print('{} ** {} = {}'.format(a, b, a ** b))

# output
4 + 3 = 7
4 - 3 = 1
4 * 3 = 12
4 / 3 = 1.33
4 % 3 = 1
4 // 3 = 1
4 ** 3 = 64

# Strings  and numbers
radius = 10
pi = 3.14
area = pi * radius ** 2
formatted_string = 'The area of radius {} is {:.2f}.'.format(radius, area) # 2 digits after decimal
print(formatted_string)

String Interpolation / f-Strings (Python 3.6+)

Another new string formatting is string interpolation, f-strings. String started with f and we can inject the data in their corresponding positions. 

a = 4
b = 3
print(f'{a} + {b} = {a +b}')
print(f'{a} - {b} = {a - b}')
print(f'{a} * {b} = {a * b}')
print(f'{a} / {b} = {a / b:.2f}') 
print(f'{a} % {b} = {a % b}')
print(f'{a} // {b} = {a // b}')
print(f'{a} ** {b} = {a ** b}')

Python strings as sequences of characters

Python strings are sequences of characters, and share their basic methods of access with those other Python sequences – lists and tuples. The simplest way of extracting single characters from strings (and individual members from any sequence) is to unpack them into corresponding variables.

Unpacking characters

language = 'Python'
a,b,c,d,e,f = language # unpacking sequence characters into variables
print(a) # P
print(b) # y
print(c) # t 
print(d) # h
print(e) # o
print(f) # n

Accessing characters in strings by index

In programming counting starts from zero. Therefore the first letter of a string is at zero index and the last letter of a string is the length of a string minus one.

String index

language = 'Python'
first_letter = language[0]
print(first_letter) # P
second_letter = language[1]
print(second_letter) # y
last_index = len(language) - 1
last_letter = language[last_index]
print(last_letter) # n
If we want to start from right end we can use negative indexing. -1 is the last index. 
language = 'Python'
last_letter = language[-1]
print(last_letter) # n
second_last = language[-2]
print(second_last) # o
  ```

#### Slicing Python Strings

In python we can slice substrings from a string.

```py
language = 'Python'
first_three = language[0:3] # starts at zero index and up to 3 but not include 3
last_three = language[3:6]
print(last_three) # hon
# Another way
last_three = language[-3:]
print(last_three)   # hon
last_three = language[3:]
print(last_three)   # hon

Reversing a string

We can easily reverse string in python.

greeting = 'Hello, World!'
print(greeting[::-1]) # !dlroW ,olleH

Skipping characters while slicing

It is possible to skip characters while slicing by passing step argument to slice method. 

language = 'Python'
pto = language[0,6:2] # 
print(pto) # Pto

String Methods

There are many string methods which allow us to format strings. See some of the string methods in the following example:

  • capitalize(): Converts the first character the string to Capital Letter 
    challenge = 'thirty days of python'
print(challenge.capitalize()) # 'Thirty days of python'
  • count(): returns occurrences of substring in string, count(substring, start=.., end=..) 
    challenge = 'thirty days of python'
print(challenge.count('y')) # 3
print(challenge.count('y', 7, 14)) # 1
print(challenge.count('th')) # 2`
  • endswith(): Checks if a string ends with a specified ending 
    challenge = 'thirty days of python'
print(challenge.endswith('on'))   # True
print(challenge.endswith('tion')) # False
  • expandtabs(): Replaces tab character with spaces, default tab size is 8. It takes tab size argument 
    challenge = 'thirty\tdays\tof\tpython'
print(challenge.expandtabs())   # 'thirty  days    of      python'
print(challenge.expandtabs(10)) # 'thirty    days      of        python'
  • find(): Returns the index of first occurrence of substring 
    challenge = 'thirty days of python'
print(challenge.find('y'))  # 5
print(challenge.find('th')) # 0
  • format() formats string into nicer output
    More about string formating check this link 
    first_name = 'Asabeneh'
last_name = 'Yetayeh'
job = 'teacher'
country = 'Finland'
sentence = 'I am {} {}. I am a {}. I live in {}.'.format(first_name, last_name, job, country)
print(sentence) # I am Asabeneh Yetayeh. I am a teacher. I live in Finland.

radius = 10
pi = 3.14
area = pi * radius ** 2
result = 'The area of circle with {} is {}'.format(str(radius), str(area))
print(result) # The area of circle with 10 is 314.0
  • index(): Returns the index of substring 
    challenge = 'thirty days of python'
print(challenge.find('y'))  # 5
print(challenge.find('th')) # 0
  • isalnum(): Checks alphanumeric character 
    challenge = 'ThirtyDaysPython'
print(challenge.isalnum()) # True

challenge = '30DaysPython'
print(challenge.isalnum()) # True

challenge = 'thirty days of python'
print(challenge.isalnum()) # False

challenge = 'thirty days of python 2019'
print(challenge.isalnum()) # False
  • isalpha(): Checks if all characters are alphabets 
    challenge = 'thirty days of python'
print(challenge.isalpha()) # True
num = '123'
print(num.isalpha())      # False
  • isdecimal(): Checks Decimal Characters 
    challenge = 'thirty days of python'
print(challenge.find('y'))  # 5
print(challenge.find('th')) # 0
  • isdigit(): Checks Digit Characters 
    challenge = 'Thirty'
print(challenge.isdigit()) # False
challenge = '30'
print(challenge.digit())   # True

  • isdecimal():Checks decimal characters 

    num = '10'
print(num.isdecimal()) # True
num = '10.5'
print(num.isdecimal()) # False

  • isidentifier():Checks for valid identifier means it check if a string is a valid variable name 

    challenge = '30DaysOfPython'
print(challenge.isidentifier()) # False, because it starts with a number
challenge = 'thirty_days_of_python'
print(challenge.isidentifier()) # True

  • islower():Checks if all alphabets in a string are lowercase 

    challenge = 'thirty days of python'
print(challenge.islower()) # True
challenge = 'Thirty days of python'
print(challenge.islower()) # False

  • isupper(): returns if all characters are uppercase characters 

    challenge = 'thirty days of python'
print(challenge.isupper()) #  False
challenge = 'THIRTY DAYS OF PYTHON'
print(challenge.isupper()) # True

  • isnumeric():Checks numeric characters 

    num = '10'
print(num.isnumeric())      # True
print('ten'.isnumeric())    # False

  • join(): Returns a concatenated string 
    web_tech = ['HTML', 'CSS', 'JavaScript', 'React']
result = '#, '.join(web_tech)
print(result) # 'HTML# CSS# JavaScript# React'
  • strip(): Removes both leading and trailing characters 
    challenge = ' thirty days of python '
print(challenge.strip('y')) # 5
  • replace(): Replaces substring inside 
    challenge = 'thirty days of python'
print(challenge.replace('python', 'coding')) # 'thirty days of coding'
  • split():Splits String from Left 
    challenge = 'thirty days of python'
print(challenge.split()) # ['thirty', 'days', 'of', 'python']
  • title(): Returns a Title Cased String 
    challenge = 'thirty days of python'
print(challenge.title()) # Thirty Days Of Python
  • swapcase(): Checks if String Starts with the Specified String The string swapcase() method converts all uppercase characters to lowercase and all lowercase characters to uppercase characters of the given string, and returns it. 
    challenge = 'thirty days of python'
print(challenge.swapcase())   # THIRTY DAYS OF PYTHON
challenge = 'Thirty Days Of Python'
print(challenge.swapcase())  # tHIRTY dAYS oF pYTHON
  • startswith(): Checks if String Starts with the Specified String 
    challenge = 'thirty days of python'
print(challenge.startswith('thirty')) # True

challenge = '30 days of python'
print(challenge.startswith('thirty')) # False

💻 Exercises - Day 4

  1. Concatenate the string 'Thirty', 'Days', 'Of', 'Python' to a single string, 'Thirty Days Of Python'
  2. Concatenate the string 'Coding', 'For' , 'All' to a single string, 'Coding For All'
  3. Declare a variable name company and assign it to an initial value "Coding For All.
  4. Print company using print()
  5. Print the length of the company string using len() method and print()
  6. Change all the characters to capital letters using upper() method
  7. Change all the characters to lowercase letters using lower() method
  8. Use capitalize(), title(), swapcase() methods to format the value the string Coding For All.
  9. Cut(slice) out the first word of Coding For All string
  10. Check if Coding For All string contains a word Coding using the method index, find or other methods.
  11. Replace the word coding in the string 'Coding For All' to Python.
  12. Change Python for Everyone to Python for All using the replace method or other methods
  13. Split the string 'Coding For All' at the space using split() method
  14. "Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon" split the string at the comma
  15. What is character at index 0 in the string Coding For All.
  16. What is the last index of the string Coding For All
  17. What character is at index 10 in "Coding For All" string.
  18. Create an acronym or an abbreviation for the name 'Python For Everyone'
  19. Create an acronym or an abbreviation for the name 'Coding For All'
  20. Use index to determine the position of the first occurrence of C in Coding For All.
  21. Use index to determine the position of the first occurrence of F in Coding For All
  22. Use rfind to determine the position of the last occurrence of l in Coding For All People.
  23. Use index or find to find the position of the first occurrence of the word because in the following sentence:'You cannot end a sentence with because because because is a conjunction'
  24. Use rindex to find the position of the last occurrence of the word because in the following sentence:'You cannot end a sentence with because because because is a conjunction'
  25. Slice out the phrase because because because in the following sentence:'You cannot end a sentence with because because because is a conjunction'
  26. Find the position of the first occurrence of the word because in the following sentence:'You cannot end a sentence with because because because is a conjunction'
  27. Slice out the phase because because because in the following sentence:'You cannot end a sentence with because because because is a conjunction'
  28. Does Coding For All starts with a substring Coding?
  29. Does Coding For All ends with a substring coding?
  30. '   Coding For All      '  , remove the left and right trailing spaces in the given string.
  31. Which one of the following variable return True when we use the method isidentifier()
    • 30DaysOfPython
    • thirty_days_of_python
  32. The following are some of python libraries list: ['Django', 'Flask', 'Bottle', 'Pyramid', 'Falcon']. Join the list with a hash with space string.
  33. Use new line escape sequence to writ the following sentence. 
    I am enjoying this challenge.
I just wonder what is next.
  34. Use a tab escape sequence to writ the following sentence. 
    Name      Age     Country
Asabeneh  250     Finland
  35. Use string formatting method to display the following: 
    radius = 10
area = 3.14 * radius ** 2
The area of radius 10 is 314 meters squares.
  36. Make the following using string formatting methods: 
    8 + 6 = 14
8 - 6 = 2
8 * 6 = 48
8 / 6 = 1.33
8 % 6 = 2
8 // 6 = 1
8 ** 6 = 262144

Day 5

Lists

The are four collection data types in python : * List: is a collection which is ordered and changeable(modifiable). Allows duplicate members. * Tuple: is a collection which is ordered and unchangeable or unmodifiable(immutable). Allows duplicate members. * Set: is a collection which is unordered and unindexed. No duplicate members. * Dictionary: is a collection which is unordered, changeable(modifiable) and indexed. No duplicate members.

A list is collection of different data types which is ordered and modifiable(mutable). A list can be empty or it may have different data type items or items

How to create a list

In python we can create list in two ways: * Using list builtin function 

# syntax
lst = list()

empty_list = list() # this is an empty list, no item in the list
print(len(empty_list)) # 0
* Using square brackets, [] 
# syntax
lst = []

empty_list = [] # this is an empty list, no item in the list
print(len(empty_list)) # 0

List with initial values. We use len() to find the length of a list. 

fruits = ['banana', 'orange', 'mango', 'lemon']                     # list of fruits
vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot']      # list of vegetables
animal_products = ['milk', 'meat', 'butter', 'yoghurt']             # list of animal products
web_techs = ['HTML', 'CSS', 'JS', 'React','Redux', 'Node', 'MongDB'] # list of web technologies
countries = ['Finland', 'Estonia', 'Denmark', 'Sweden', 'Norway']

# Print the lists and it length
print('Fruits:', fruits)
print('Number of fruits:', len(fruits))
print('Vegetables:', vegetables)
print('Number of vegetables:', len(vegetables))
print('Animal products:',animal_products)
print('Number of animal products:', len(animal_products))
print('Web technologies:', web_techs)
print('Number of web technologies:', len(web_techs))
print('Countries:', countries)
print('Number of countries:', len(countries))

output
Fruits: ['banana', 'orange', 'mango', 'lemon']
Number of fruits: 4
Vegetables: ['Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']
Number of vegetables: 5
Animal products: ['milk', 'meat', 'butter', 'yoghurt']
Number of animal products: 4
Web technologies: ['HTML', 'CSS', 'JS', 'React', 'Redux', 'Node', 'MongDB']
Number of web technologies: 7
Countries: ['Finland', 'Estonia', 'Denmark', 'Sweden', 'Norway']
Number of countries: 5
* List can have items of different data types 
 lst = ['Asabeneh', 250, True, {'country':'Finland', 'city':'Helsinki'}] # list containing different data types

Accessing list items using positive indexing

We access each item in a list using their index. A list index start from 0. The picture below show clearly where the index starts List index 

fruits = ['banana', 'orange', 'mango', 'lemon'] 
first_fruit = fruits[0] # we are accessing the first item using its index
print(first_fruit)      # banana
second_fruit = fruits[1]
print(second_fruit)     # orange
last_fruit = fruits[3]
print(last_fruit) # lemon
# Last index
last_index = len(fruits) - 1
last_fruit = fruits[last_index]

Accessing list items using negative indexing

Negative indexing means beginning from the end, -1 refers to the last item, -2 refers to the second last item.

List negative indexing 

fruits = ['banana', 'orange', 'mango', 'lemon']
first_fruit = fruits[-4]
last_fruit = fruits[-1]
second_last = fruits[-2]
print(first_fruit)      # banana
print(last_fruit)       # lemon
print(second_last)      # mango

Unpacking list items

lst = ['item','item2','item3', 'item4', 'item5']
first_item, second_item, third_item, *rest = lst
print(first_item)     # item1
print(second_item)    # item1
print(third_item)     # item2
print(rest)           # ['item4', 'item5']

# First Example
fruits = ['banana', 'orange', 'mango', 'lemon','lime','apple']
first_fruit, second_fruit, third_fruit, *rest = lst
print(first_fruit)     # banana
print(second_fruit)    # orange
print(third_fruit)     # mango
print(rest)           # ['lemon','lime','apple']
# Second Example about unpacking list
first, second, third,*rest, tenth = [1,2,3,4,5,6,7,8,9,10]
print(first)
print(second)
print(third)
print(rest)
print(tenth)
# Third Example about unpacking list
countries = ['Germany', 'France','Belgium','Sweden','Denmark','Finland','Norway','Iceland','Estonia']
gr, fr, bg, sw, *scandic, es = countries
print(gr)
print(fr)
print(bg)
print(sw)
print(scandic)
print(es)

Slicing items from list

  • Positive Indexing: We can specify a range of positive indexes by specifying the starting and the ending, the return value will be a new list. 
    fruits = ['banana', 'orange', 'mango', 'lemon'] 
all_fruits = fruits[0:4] # it returns all the fruits
# this is also give the same result as the above
all_fruits = fruits[0:] # if we don't set where to stop it takes all the rest
orange_and_mango = fruits[1:3] # it does not include the end index
orange_mango_lemon = fruits[1:]
  • Negative Indexing: We can specify a range of negative indexes by specifying the starting and the ending, the return value will be a new list. 
    fruits = ['banana', 'orange', 'mango', 'lemon'] 
all_fruits = fruits[-4:] # it returns all the fruits
# this is also give the same result as the above
orange_and_mango = fruits[-3:-1] # it does not include the end index
orange_mango_lemon = fruits[-3:]

Modifying list

List is a mutable or modifiable ordered collection of items or items. Lets modify the fruit list. 

fruits = ['banana', 'orange', 'mango', 'lemon'] 
fruits[0] = 'Avocado' 
print(fruits)       #  ['avocado', 'orange', 'mango', 'lemon']
fruits[1] = 'apple'
print(fruits)       #  ['avocado', 'apple', 'mango', 'lemon']
last_index = len(fruits)
fruits[last_index] = 'lime'
print(fruits)        #  ['avocado', 'apple', 'mango', 'lime']

Check items in a list

fruits = ['banana', 'orange', 'mango', 'lemon']
does_exist = 'banana' in fruits
print(does_exist)  # True
does_exist = 'lime' in fruits
print(does_exist)  # False

Adding item in a list

To add item to the end of an existing list we use the method 

# syntax
lst = list()
lst.append(item)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.append('apple')
print(fruits)           # ['banana', 'orange', 'mango', 'lemon', 'apple']
fruits.append('lime')   # ['banana', 'orange', 'mango', 'lemon', 'apple', 'lime']
print(fruits)

Inserting item in to a list

Use insert() method to insert a single item at a specified index in a list. Note that other items are shifted to the right. 

# syntax
lst = ['item1', 'item2']
lst.insert(index, item)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.insert(2, 'apple') # insert apple between orange and mango
print(fruits)           # ['banana', 'orange', 'apple', 'mango', 'lemon']
fruits.insert(3, 'lime')   # ['banana', 'orange', 'apple', 'mango', 'lime','lemon']
print(fruits)

Removing item from list

The remove method remove a specified item from a list 

# syntax
lst = ['item1', 'item2']
lst.remove(item)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.remove('banana')
print(fruits)  # ['orange', 'mango', 'lemon']
fruits.remove('lemon')
print(fruits)  # ['orange', 'mango']

Removing item using pop

The pop() method removes the specified index, (or the last item if index is not specified): 

# syntax
lst = ['item1', 'item2']
lst.pop()       # last item
lst.pop(index)

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.pop()     
print(fruits)       # ['banana', 'orange', 'mango']

fruits.remove(0)     
print(fruits)       # ['orange', 'mango']

Removing item using del

The del keyword removes the specified index and it can be also use to delete the list completely

# syntax
lst = ['item1', 'item2']
del lst[index] # only a single item
del lst        # to delete the list completely

fruits = ['banana', 'orange', 'mango', 'lemon']
del fruits[0]     
print(fruits)       # ['orange', 'mango', 'lemon']

del fruits[1]     
print(fruits)       # ['orange', 'lemon']
del fruits
print(fruits)       # This should give: NameError: name 'fruits' is not defined

Clearing list items

The clear() method empties the list: 

# syntax
lst = ['item1', 'item2']
lst.clear()

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.clear()     
print(fruits)       # []

Copying a list

It is possible to copy a list by reassigning to a new variable in the following way list2 = list1. Now, list2 is a reference of list1, any changes we make in list2 will also modify the original, list2. But there are lots of case in which we do not like to modify the original instead we like to have a different copy. One of way avoid the above problem is using copy(). 

# syntax
lst = ['item1', 'item2']
lst_copy = lst.copy()

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits_copy = fruits.copy()     
print(fruits_copy)       # ['banana', 'orange', 'mango', 'lemon']

Joining lists

There are several ways to join, or concatenate, two or more lists in Python.

  • Plus Operator (+) 
    # syntax
list3 = list1 +list2

    positive_numbers = [1, 2, 3,4,5]
zero = [0]
negative_numbers = [-5,-4,-3,-2,-1]
integers = negative_numbers + zero + positive_numbers
print(integers)
fruits = ['banana', 'orange', 'mango', 'lemon']
vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot'] 
fruits_and_vegetables = fruits + vegetables
print(fruits_and_vegetables )

    # output
[-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
['banana', 'orange', 'mango', 'lemon', 'Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']
  • Joining using extend() method

# syntax
lst1 = ['item1', 'item2']
lst2 = ['item3', 'item4','item5']
list1.extend(list2)

num1 = [0, 1, 2, 3]
num2= [4, 5,6]
num1.extend(num2)
print('Numbers:', num1)
negative_numbers = [-5,-4,-3,-2,-1]
positive_numbers = [1, 2, 3,4,5]
zero = [0]

negative_numbers.extend(zero)
negative_numbers.extend(positive_numbers)
print('Integers:', negative_numbers)
fruits = ['banana', 'orange', 'mango', 'lemon']
vegetables = ['Tomato', 'Potato', 'Cabbage','Onion', 'Carrot'] 
fruits.extend(vegetables)
print('Fruits and vegetables:', fruits )

Numbers: [0, 1, 2, 3, 4, 5, 6]
Integers: [-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5]
Fruits and vegetables: ['banana', 'orange', 'mango', 'lemon', 'Tomato', 'Potato', 'Cabbage', 'Onion', 'Carrot']

Counting Items in a list

The count() method returns the number of times an item appears in a list: 

# syntax
lst = ['item1', 'item2']
lst.count(item) 

fruits = ['banana', 'orange', 'mango', 'lemon']
print(fruits.count('orange'))   # 1
ages = [22, 19, 24, 25, 26, 24, 25, 24]
print(ages.count(24))           # 3

Finding index of an item

The count() method returns the index of an item in the list: 

# syntax
lst = ['item1', 'item2']
lst.index(item) 

fruits = ['banana', 'orange', 'mango', 'lemon']
print(fruits.index('orange'))   # 1
ages = [22, 19, 24, 25, 26, 24, 25, 24]
print(ages.index(24))           # 2, the first occurrence

Reversing a list

The reverse() method reverse the order of a list. 

# syntax
lst = ['item1', 'item2']
lst.reverse() 

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.reverse()
print(fruits.reverse())  
ages = [22, 19, 24, 25, 26, 24, 25, 24]
ages.reverse()
print(ages.reverse())         

['lemon', 'mango', 'orange', 'banana']
[24, 25, 24, 26, 25, 24, 19, 22]

Sorting list items

To sort list we can use sort() method or sorted() builtin function. The sort() method reorder the list items in ascending order and modify the original list. If a reverse is equal to true it arrange in descending order. * sort(): 

# syntax
lst = ['item1', 'item2']
lst.sort()                # ascending
lst.sort(reverse=True)    # descending
Example:*

fruits = ['banana', 'orange', 'mango', 'lemon']
fruits.sort()
print(fruits) 
fruits.sort(reverse=True)
print(fruits)
ages = [22, 19, 24, 25, 26, 24, 25, 24]
ages.sort()
print(ages) 
ages.sort(reverse=True)
print(ages)           

['banana', 'lemon', 'mango', 'orange']
['orange', 'mango', 'lemon', 'banana']
[19, 22, 24, 24, 24, 25, 25, 26]
[26, 25, 25, 24, 24, 24, 22, 19]
sorted(): returns the ordered list without modifying the original Example: py fruits = ['banana', 'orange', 'mango', 'lemon'] fruits = sorted(fruits) print(fruits) # ['banana', 'lemon', 'mango', 'orange'] # Reverse order fruits = ['banana', 'orange', 'mango', 'lemon'] fruits = sorted(fruits,reverse=True) print(fruits) # ['orange', 'mango', 'lemon', 'banana']

💻 Exercises: Day 5

  1. Declare an empty list
  2. Declare a list with more than 5 number of items
  3. Find the length of your list
  4. Get the first item, the middle item and the last item of the list
  5. Declare a list called mixed_data_types,put your(name, age, height, marital status, address)
  6. Declare a list variable name it_companies and assign initial values Facebook, Google, Microsoft, Apple, IBM, Oracle and Amazon.
  7. Print the list using print()
  8. Print the number of companies in the list
  9. Print the first, middle and last company
  10. Print modify any of the companies
  11. Add an IT company to it_companies
  12. Insert an IT company in the middle of the companies list
  13. Change one of the it_companies item to uppercase
  14. Join the it_companies with a string '#;  '
  15. Check if a certain company exists in the it_companies list.
  16. Sort the list using sort() method
  17. Reverse the list in descending order using reverse() method
  18. Slice out the first 3 companies from the list
  19. Slice out the last 3 companies from the list
  20. Slice out the middle IT company or companies from the list
  21. Remove the first IT company from the list
  22. Remove the middle IT company or companies from the list
  23. Remove the last IT company from the list
  24. Remove all IT companies item
  25. Destroy the IT companies list
  26. Join the following lists: 
    front_end = ['HTML', 'CSS', 'JS', 'React', 'Redux']
back_end = ['Node','Express', 'MongoDB']
  27. After joining the lists in question 26. Copy the joined list and assigned it to a variable full_stack. Then insert, Python and SQL after Redux.
  28. The following is a list of 10 students ages: 
    ages = [19, 22, 19, 24, 20, 25, 26, 24, 25, 24]
  29. Sort the list and find the min and max age
  30. Add the min age and the max age
  31. Find the median age(one middle item or two middle items divided by two)
  32. Find the average age(all items divided by number of items)
  33. Find the range of the ages(max minus min)
  34. Compare the value of (min - average) and (max - average), use abs() method
  35. Find the middle country(ies) in the countries list
  36. Divide the countries list into two equal lists if it is even if not one more country for the first half.
  37. ['China', 'Russia', 'USA', 'Finland', 'Sweden', 'Norway', 'Denmark']. Unpack the first three countries and the rest as scandic countries.

Day 6:

Tuple

A tuple is a collection of different data types which is ordered and unchangeable(immutable). Tuples are written with round brackets,(). Once a tuple is created, we can not change its values. We can not add, insert, remove a tuple because it is not modifiable (mutable). Unlike list, tuple has few methods. Methods related to tuple: * tuple(): to create an empty tuple * count(): to count the number of a specified item in a tuple * index(): to find the index of a specified item in a tuple * + operator: to join two or more tuples and to create new tuple

Creating Tuple

  • Empty tuple: Creating an empty tuple 
    # syntax
empty_tuple = () 
# or using the tuple constructor
empty_tuple = tuple()
  • Tuple with initial values 
    # syntax
tpl = ('item1', 'item2','item3')

  • fruits = ('banana', 'orange', 'mango', 'lemon')

Tuple length

We use the len() method to get the length of a tuple. 

# syntax
tpl = ('item1', 'item2', 'item3')
len(tpl)

Accessing tuple items

  • Positive Indexing Similar to the list data type we use positive or negative indexing to access tuple items. Accessing tuple items

# Syntax
tpl = ('item1', 'item2', 'item3')
first_item = tpl[0]
second_item = tpl[1]

fruits = ('banana', 'orange', 'mango', 'lemon')
first_fruit = fruits[0]
second_fruit = fruits[1]
last_index =len(fruits) - 1
last_fruit = fruits[las_index]
* Negative indexing Negative indexing means beginning from the end, -1 refers to the last item, -2 refers to the second last and the negative of the list length refers to the first item. Tuple Negative indexing 
# Syntax
tpl = ('item1', 'item2', 'item3','item4')
first_item = tpl[-4]
second_item = tpl[-3]

fruits = ('banana', 'orange', 'mango', 'lemon')
first_fruit = fruits[-4]
second_fruit = fruits[-3]
last_fruit = fruits[-1]

Slicing tuples

We can slice out a sub tuple by specifying a range of indexes where to start and where to end in the tuple, the return value will be a new tuple with the specified items.

  • Range of Positive Indexes

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
all_items = tpl[0:4]         # all items
all_items = tpl[0:]         # all items
middle_two_items = tpl[1:3]  # does not include item at index 3

fruits = ('banana', 'orange', 'mango', 'lemon')
all_fruits = fruits[0:4]    # all items
all_fruits= fruits[0:]      # all items
orange_mango = fruits[1:3]  # doesn't include item at index 3
orange_to_the_rest = fruits[1:]

  • Range of Negative Indexes

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
all_items = tpl[-4:]         # all items
middle_two_items = tpl[-3:-1]  # does not include item at index 3

fruits = ('banana', 'orange', 'mango', 'lemon')
all_fruits = fruits[-4:]    # all items
orange_mango = fruits[-3:-1]  # doesn't include item at index 3
orange_to_the_rest = fruits[-3:]

Changing tuples to list

We can change tuples to list and list to tuple. Tuple is immutable if we want to modify a tuple we should change to a list. 

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
lst = list(tpl)

fruits = ('banana', 'orange', 'mango', 'lemon')
fruits = list(fruits)
fruits[0] = 'apple'
print(fruits)     # ['apple', 'orange', 'mango', 'lemon']
fruits = tuple(fruits)
print(fruits)     # ('apple', 'orange', 'mango', 'lemon')

Checking an item in a list

We can check an item if it exists in a list or not using in, it returns boolean. 

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
'item2' in tpl # True

fruits = ('banana', 'orange', 'mango', 'lemon')
'orange' in fruits # True
'apple' in fruits # False
fruits[0] = 'apple'

Joining tuples

We can join two or more tuples using + operator 

# syntax
tpl1 = ('item1', 'item2', 'item3')
tpl2 = ('item4', 'item5','item6')
tpl3 = tpl1 + tpl2

fruits = ('banana', 'orange', 'mango', 'lemon')                    
vegetables = ('Tomato', 'Potato', 'Cabbage','Onion', 'Carrot')
fruits_and_vegetables = fruits + vegetables

Deleting tuple

It is not possible to remove a single item in a tuple but it is possible to delete the tuple itself using del. 

# syntax
tpl1 = ('item1', 'item2', 'item3')
del tpl1

fruits = ('banana', 'orange', 'mango', 'lemon') 
del fruits

💻 Exercises: Day 6

  1. Create an empty tuple
  2. Create a tuple containing name of your sisters and your brothers
  3. Join brothers and sisters tuples and assign it to siblings
  4. How many siblings do you have ?
  5. Modify the siblings tuple and add the name of your father and mother and assign it to family_members
  6. Unpack siblings and parents from family_members
  7. Create a fruits, vegetables and animal products tuples. Join the three tuples and assign it to a variable called food_stuff.
  8. Slice out the middle item or items from the food_staff list
  9. Slice out the first three items and the last three items from food_staff list
  10. Delete the food_staff list completely
  11. Check if an item exist in a tuple:
  12. Check if 'Estonia' is a nordic country
  13. Check if 'Iceland' is a nordic country 
    nordic_countries = ('Denmark', 'Finland','Iceland', 'Norway', 'Sweden')

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