Python Notes - Part 02

  1. What is a for loop?
    • A way by which a task can be repeated through a LIST/TUPLE/DICTIONARY without needing to repeat the task request.
    • Example:
    • list = [‘1’, ‘2’, ‘3’, ‘4’]
    • for number in list:
    •       print(“My favorite number is “ + number + “.”)

    >>> My favorite number is 1.

    >>> My favorite number is 2.

    >>> My favorite number is 3.

    >>> My favorite number is 4.

    Print function will run through each item in the list.
  2. How does the range() method work?
    Generates a series of numbers.

    • Example:
    • for value in range(1,5):

            Print(value)

    • >>>1
    • >>>2
    • >>>3
    • >>>4

    Range() output never contains the end parameter (5 in this case).
  3. How does the list() method work?
    Creates a list.

    • Example:
    • numbers = list(range(1,6))
    • >>>print(numbers)
    • >>>[1, 2, 3, 4, 5]
  4. How can you create intervals (skips) with the range() method?
    • Example:
    • range(2,11,2)
    • # Range begins at 2 and continues till 10 and adds 2 at every number
    • >>>list(range(2,11,2)
    • >>>print(list)
    • >>>[2, 4, 6, 8, 10]
  5. How can you find the minimum, maximum and sum total of a list?
    Use the min(), max() and sum() methods.

    • Example:
    • >>>list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]
    • >>>min(list)
    • >>>0
    • >>>max(list)
    • >>>9
    • >>>sum(list)
    • >>>45
  6. What is slicing in regards to lists?
    Accessing specifics items from a list.

    • Example:
    • list = [‘charles’, ‘martina’, ‘michael’, ‘florence’, ‘eli’]
    • >>>print(list[0:3])
    • >>>[‘charles’, ‘martina’, ‘michael’]
    • >>>print(list[1:4])
    • >>>[‘martina’, ‘michael’, ‘florence’]
    • >>>print(list[:3] # this signifies that the list starts from the very beginning
    • >>>[‘charles’, ‘martina’, ‘michael’]
    • >>>print(list[-3:])
    • >>>[‘michael’, ‘florence’, ‘eli’]
  7. How do you copy a list?
    • Example:
    • list = [‘pizza’, ‘pasta’, ‘sushi’, ‘hamburger’]
    • food = list[:] # new list variable must always be the first placed to create a copy
    • >>>print(food)
    • [‘pizza’, ‘pasta’, ‘sushi’, ‘hamburger’]
  8. What is a Tuple?
    A container for multiple items.

    • A tuple looks just like a list except you use parentheses instead of square brackets
    • The items within the Tuple cannot be modified (no removal, exchange or addition)

    • Example:
    • numbers = (200, 50)
    • Only way to modify a tuple is to assign a new series of items to the tuple
    • numbers = (400, 100)
  9. What is a Conditional Expression?
    A way to compare/evaluate an if statement.

    • in
    • and
    • or
    • not in
    • is
    • is not

  10. What are Comparison Operators?
    Operators that compare two values.

    • ==    (Equal to)
    • !=     (Not equal to)
    • <      (Less than)
    • >      (Greater than)
    • <=   (Less than or equal to)
    • >=   (Greater than or equal to)

  11. What is an if statement?
    A conditional that, when it is satisfied, activates some part of a code.

    • Example:
    • >>>a = 20
    • >>>if a >= 22:
    •              print(“if”)
    •       elif a >= 21:
    •              print(“elif”)
    •       else:
    •              print(“else”)

  12. What is a Dictionary?
    • Location where related data are placed.
    • Operate as key-value pairs
    • Curly braces { } mark the beginning and end of a Dictionary.
    • Example:
    • person = {‘first name’: ‘paul’, ‘last name’: ‘smith’, ‘age’: 23}
    • words on the left are the keys
    • words / number on the right are the value

    • >>>print(person[‘first name’])
    • >>>’paul’
  13. Can a value in a Dictionary be changed/modified?
    • Values can be changed/modified
    • Example:
    • person = {‘first name’: ‘paul’, ‘last name’: ‘smith’, ‘age’: 23}
    • person[‘first name’] = ‘gary’
    • >>>print(person[‘first name’])
    • >>>’gary’
  14. Can a Key-Value pair be removed from a Dictionary?
    • Key-Value pairs can be removed from a Dictionary
    • Example: # use del method
    • person = {‘first name’: ‘paul’, ‘last name’: ‘smith’, ‘age’: 23}
    • del person[‘first name’]
    • >>>print(person)
    • >>>{‘last name’: ‘smith’, ‘age’: 23}
  15. Can a For Loop be used on a Dictionary?
    • For Loop can be used on a Dictionary.
    • Example:
    • user_0 = {'username': 'efermi', 'first': 'enrico','last': 'fermi',}
    • for key, value in user_0.items():
    • print("\nKey: " + key)
    • print("Value: " + value)
    • Using the items() method permits the For Loop to go through the keys and values in the Dictionary
    • The key is contained within the (key) variable, the value is contained within the (value) variable

    • Key: username
    • Value: efermi

    • Key: first
    • Value: enrico

    • Key: last
    • Value: fermi
  16. How can you loop through all the keys in Dictionary?
    • Using the For Loop and the keys() method
    • Example:
    • favorite_languages = {'jen': 'python', 'sarah': 'c', 'edward': 'ruby',
    • 'phil': 'python',}
    • for name in favorite_languages.keys():
    • print(name.title())
    • >>>Jen
    • >>>Sarah
    • >>>Phil
    • >>>Edward
    • Note: Looping through the keys is actually the default behavior when looping through a dictionary. Code could be written as such:
    • for name in favorite_languages:
  17. How can the Dictionary keys be sorted when processed in a For Loop?
    • Using the sorted() method
    • Example:
    • favorite_languages = {'jen': 'python', 'sarah': 'c', 'edward': 'ruby',
    • 'phil': 'python',}
    • for name in sorted(favorite_languages.keys()):
    • print(name.title())
    • >>>Edward
    • >>>Jen
    • >>>Phil
    • >>>Sarah
  18. How can you loop through all the values in a Dictionary?
    • Using the For Loop and the values() method
    • Example:
    • favorite_languages = {'jen': 'python', 'sarah': 'c', 'edward': 'ruby',
    • 'phil': 'python',}
    • for language in favorite_languages.values():
    • print(language.title())
    • >>>Python
    • >>>C
    • >>>Ruby
    • >>>Python
  19. How can you loop through a Dictionary and not include the repeated values?
    • Using the set() method
    • Example:
    • favorite_languages = {'jen': 'python', 'sarah': 'c', 'edward': 'ruby',
    • 'phil': 'python',}
    • for language in se(favorite_languages.values()):
    • print(language.title())
    • >>>Python
    • >>>C
    • >>>Ruby
  20. What is nesting?
    • When a list, tuple, dictionary are placed within other lists, tuples or dictionaries.
    • # Dictionaries in a list
    • alien_0 = {'color': 'green', 'points': 5}
    • alien_1 = {'color': 'yellow', 'points': 10}
    • alien_2 = {'color': 'red', 'points': 15}
    • aliens = [alien_0, alien_1, alien_2]

    • # List in a Dictionary
    • pizza = {'crust': 'thick', 'topping : ['mushrooms', 'extra cheese'],}

    • # Dictionary in a Dictionary
    • users = {'aeinstein': {'first': 'albert', 'last': 'einstein', 'location': 'princeton',}
Author
faker1010
ID
342594
Card Set
Python Notes - Part 02
Description
Python Notes - Part 02
Updated