Python Notes - Part 01

• Variables are used to store values. A string is a series of characters, surrounded by single or double quotes.
• Example: age = 23
• The Integer 23 is stored in the Variable age

Variable names can contain only letters, numbers, and underscores. They can start with a letter or an underscore, but not with a number. For instance, you can call a variable message_1 but not 1_message.

Spaces are not allowed in variable names, but underscores can be used to separate words in variable names. For example, greeting message works, but greeting message will cause errors.

• String: (Example: “Joey Marley”)
• Numbers: (Intergers and Floats)
• Complex numbers:  (2 + 3j)
• Boolean (True or False)
• Lists: test =  ['a', 'b', 'c']
• Tuples: test = (1, 2, 3)
• Dictionaries: test = {'Name': 'Zara', 'Age': 7, 'Class': 'First'}

PEMDAS

• A character that allows the following element to not follow a set rule
• Example: string = ‘I don\’t love Mondays.’
• Example of Escape Sequences
• \n and   \t

A record of where the interpreter ran into trouble when trying to execute your code.

• Using the title() method
• string = “jOeY mArLeY”
• >>>print(string.title())
• >>>“Joey Marley”

• Uppercase: upper()
• string = “jOeY mArLeY”
• >>>print(string.upper())
• >>>“JOEY MARLEY”

• Lowercase: lower()
• string = “jOeY mArLeY”
• >>>print(string.lower())
• >>>“joey marley”

• Notes left within the code the are not processed
• Left as reminder/explanations for the code

• A list is a collection of items in a particular order.
• In Python, square brackets ( [] ) indicate a list, and individual elements in the list are separated by commas.
• Items in the List are indexed starting from zero (0, 1, 2, 3) and left to right.
• Example:
• list = [‘car’, ‘boat’,  ‘plane’,  ‘train’]

• list = [‘car’, ‘boat’,  ‘plane’,  ‘train’]
• >>>print(list[1])
• >>>boat
• >>>print(list[0])
• >>>car

• Negative numbers start from the end of the list (-1, -2, -3, -4) / no zero
• >>>print(list[-1])
• >>>train
• >>>print(list[-2]
• >>>plane

• list = [‘honda’, ‘yamaha’,  ‘suzuki’]
• list[1] = ‘toyota’
• >>>print(list)
• >>>[‘honda’, ‘toyota’,  “suzuki’]

• Using the append() method
• list = [‘honda’, ‘yamaha’,  ‘suzuki’]
• list.append(‘ducati’)
• >>>print(list)
• >>>[‘honda’, ‘yamaha’, ‘suzuki’, ‘ducati’]
• The append() method adds the item to the end of the list

• Using the insert() method
• list = [‘honda’, ‘yamaha’, ‘suzuki’]
• list.insert(0, ‘ducati’)
• >>>print(list)
• >>>[‘ducati’, ‘honda’, ‘yamaha’, ‘suzuki’]

• Using the del method
• list = [‘honda’, ‘yamaha’, ‘suzuki’]
• del list[0]
• >>>print(list)
• [‘yamaha’, ‘suzuki’]

• Using the pop.() method
• list = [‘honda’, ‘yamaha’, ‘suzuki’]
• popped_item = list.pop()
• >>>print(list)
• [‘honda’, ‘yamaha’]
• >>>print(popped_item)
• >>>’suzuki’
• If not defined, the pop() method will remove the last item from the list (see above)
• popped_item = list.pop(1)
• >>>print(list)
• [‘honda’, ‘suzuki’]
• >>>print(popped_item)
• >>>’yamaha’

• Using the remove() method
• list = [‘honda’, ‘yamaha’, ‘suzuki’, ‘ducati’]
• list.remove(‘ducati’)
• >>>print(list)
• >>>[‘honda’, ‘yamaha’, ‘suzuki’]

• Using the sort() method
• list = [‘b’, ‘d’, ‘a’, ‘c’]
• list.sort()
• >>>print(list)
• >>>[‘a’, ‘b’, ‘c’, ‘d’]
• list cannot be reverted to its original order after the sort() method is used

• Using the sort() method with reverse=True in the parentheses
• list = [‘b’, ‘d’, ‘a’, ‘c’]
• list.sort(reverse=True)
• >>>print(list)
• >>>[‘d’, ‘c’, ‘b’, ‘a’]
• list cannot be reverted to its original order after reverse sorting

• Using the sorted() method
• list = [‘b’, ‘d’, ‘a’, ‘c’]
• >>>print(sorted(list))
• >>>[‘a’, ‘b’, ‘c’, ‘d’]
• >>> print(list)
• >>>[‘b’, ‘d’, ‘a’, ‘c’]
• Temporary sorting order can also be reversed
• >>>print(sorted(list, reverse=True))
• >>>[‘d’, ‘c’, ‘b’, ‘a’]
• >>>print(list)
• >>>[‘b’, ‘d’, ‘a’, ‘c’]

• Using the reverse() method
• list = [‘b’, ‘d’, ‘a’, ‘c’]
• list.reverse()
• >>>print(list)
• >>>[‘c’, ‘a’, ‘d’, ‘b’]

• Using the len() method
• list = [‘b’, ‘d’, ‘a’, ‘c’]
• >>>print(len(list))
• >>>4