Python Data Structures

Strings

fruit = “string”

• Can use in as a logical operator for strings
• String Comparison → == , >, > (measures if something comes before or after it)
• string methods:
  • string.lower() → Gives us a copy of a string
  • string.upper() → Gives us a copy of a string, all uppercase

• Find → Finds the first occurrence of the sub-string (sub-string, start-from, end)
• replace() → Search and replace: greet.replace(’Bob’, ‘jane’)
• lstrip(), rstrip(), strip() → removes the trailing white spaces (left, right, and both) also removes new lines!
• startswith() → Gives us a T/F based on if a string starts with the substring

Lists

• Reversing a list example w/ list indices

  • nums = [1,2,3,4]

  • nums[::-1] will reverse the list!

    In Python, the expression nums[::-1] is used to reverse a list or any other sequence. Let's break it down:

    • nums refers to the list that you want to reverse.
    • The first colon : indicates that you want to select a slice of the list.
    • The second colon : is used to specify the step size. In this case, the step size is 1, which means you want to traverse the list in reverse order.
    • The [::-1] part specifies the start and end indices for the slice. Since no start or end indices are provided, the default values are used, which means you want to select the entire list.

Dictionaries / Hash maps (Python)

• Bag of words, key, value collection.
• purse = dict()
• purse[’money’] = 12
• purse[’candy’] = 3
• print(money)
• #Updating a value
  • purse[’candy’] = purse[’candy’] + 2 # This is now a 5