Python Language Fundamentals

Variables & Data Types In Python

# A variable is a container for a value, which can be of various types

'''

This is a

multiline comment

or docstring (used to define a function's purpose)

can be single or double quotes

'''

"""

VARIABLE RULES:

  - Variable names are case sensitive (name and NAME are different variables)

  - Must start with a letter or an underscore

  - Can have numbers but can not start with one

"""

# x = 1           # int
# y = 2.5         # float
# name = 'John'   # str
# is_cool = True  # bool

# Multiple assignments

x, y, name, is_cool = (1, 2.5, 'John', True)

# Basic math

a = x + y

# Casting

x = str(x)
y = int(y)
z = float(y)

print(type(z), z)

Strings & Formatting

# Strings in Python are surrounded by either single or double quotation marks. Let's look at string formatting and some string methods

name = 'John'
age = 37

# Concatenate

print('Hello, my name is ' + name + ' and I am ' + str(age))

# String Formatting

# Arguments by position

print('My name is {name} and I am {age}'.format(name=name, age=age))

# F-Strings (3.6+)

print(f'Hello, my name is {name} and I am {age}')

# String Methods

s = 'hello world'

# Capitalize string

print(s.capitalize())

# Make all uppercase

print(s.upper())

# Make all lower

print(s.lower())

# Swap case

print(s.swapcase())

# Get length

print(len(s))

# Replace

print(s.replace('world', 'everyone'))

# Count

sub = 'h'
print(s.count(sub))

# Starts with

print(s.startswith('hello'))

# Ends with

print(s.endswith('d'))

# Split into a list

print(s.split())

# Find position

print(s.find('r'))

# Is all alphanumeric

print(s.isalnum())

# Is all alphabetic

print(s.isalpha())

# Is all numeric

print(s.isnumeric())

Python List

# A List is a collection that is ordered and changeable. Allows duplicate members.

# Create list

numbers = [1, 2, 3, 4, 5]
fruits = ['Apples', 'Oranges', 'Grapes', 'Pears']

# Use a constructor

# numbers2 = list((1, 2, 3, 4, 5))

# Get a value

print(fruits[1])

# Get length

print(len(fruits))

# Append to list

fruits.append('Mangos')

# Remove from the list

fruits.remove('Grapes')

# Insert into position

fruits.insert(2, 'Strawberries')

# Change value

fruits[0] = 'Blueberries'

# Remove with pop

fruits.pop(2)

# Reverse list

fruits.reverse()

# Sort list

fruits.sort()

# Reverse sort
fruits.sort(reverse=True)

print(fruits)

Python Tuples

# A Tuple is a collection that is ordered and unchangeable. Allows duplicate members.

# Create tuple

fruits = ('Apples', 'Oranges', 'Grapes')

# Using a constructor

# fruits2 = tuple(('Apples', 'Oranges', 'Grapes'))

# Single value needs trailing comma

fruits2 = ('Apples',)

# Get value

print(fruits[1])

# Can't change the value

fruits[0] = 'Pears'

# Delete tuple

del fruits2

# Get length

print(len(fruits))

Python Sets

# A Set is a collection that's unordered and unindexed. No duplicate members.

# Create set

fruits_set = {'Apples', 'Oranges', 'Mango'}

# Check if in set

print('Apples' in fruits_set)

# Add to set

fruits_set.add('Grape')

# Remove from set

fruits_set.remove('Grape')

# Add duplicate

fruits_set.add('Apples')

# Clear set

fruits_set.clear()

# Delete

del fruits_set

print(fruits_set)