Python Hello World Example

  # This is a simple Hello, World! program in Python.
  # The print function is used to display text on the screen
  
  print("Hello, World!")

Commenting in Python

  # Example of variable assignments
  x = 5 # variable x with integer value 5

  name = "John Doe" # variable name with string value "John Doe"
  pi = 3.14 # variable pi with float value 3.14

  # Changing the value of a variable
  x = 5

  print(x) # prints 5
  x = 10

  print(x) # prints 10

  x = 5 # x is an integer
  x = "hello" # x is now a string
  x = [1, 2, 3] # x is now a list

  # Good variable names
  first_name = "John"
  last_name = "Doe"
  average_temperature = 72.5

  # Bad variable names
  x = "John"
  y = "Doe"
  z = 72.5

Python Datatypes

  x = 5
  y = 2

  # addition
  print(x + y) # 7

  # subtraction
  print(x - y) # 3

  # multiplication
  print(x * y) # 10

  # division
  print(x / y) # 2.5

  # modulus
  print(x % y) # 1

  x = 5
  y = 2

  x += y # x = x + y

  x -= y # x = x - y

  x *= y # x = x * y

  x /= y # x = x / y

  x %= y # x = x % y

  x = 5
  y = 2

  print(x == y) # False

  print(x != y) # True

  print(x > y) # True

  print(x = y) # True

  print(x 

  x = True
  y = False

  print(x and y) # False

  print(x or y) # True

  print(not x) # False

  x = [1, 2, 3]
  y = [1, 2, 3]
  z = x

  print(x is y) # False

  print(x is z) # True

  print(x is not y) # True      

  x = [1, 2, 3]
  y = 2

  print(y in x) # True

  print(y not in x) # False

Python Loops

For Loops

numbers = [1, 2, 3, 4, 5]

for num in numbers:
    print(num)        

while condition: # code to be executed

counter = 0

while counter     

for num in range(10):
    if num == 5:
        break
    print(num)

for num in range(10):
    if num % 2 == 0:
        continue
    print(num)

for num in range(10):
    if num % 2 == 0:
        pass
    else:
        print(num)

Integers

Floating-point numbers

Complex numbers

Boolean

• int() - converts a number or a string to an integer
• float() - converts a number or a string to a floating-point number
• complex() - creates a complex number from a real and an imaginary component
• bool() - converts a value to a Boolean

Example:

x = 5
y = 2.5
z = 1 + 2j

a = int(y)

b = float(x)

c = complex(x, y)

d = bool(z)

fruits = ["apple", "banana"]
more_fruits = ["orange", "mango"]

all_fruits = fruits + more_fruits

print(all_fruits) # ['apple', 'banana', 'orange', 'mango']


fruits = ["apple"]

print(fruits * 3) # ['apple', 'apple', 'apple']

• append(item) adds an item to the end of the list.

• insert(index, item) inserts an item at the specified index.

• remove(item) removes the first occurrence of the specified item.

• pop() removes the item at the specified index (if no index is specified, the last item is removed).

• sort() sorts the items of the list in ascending order.

• reverse() reverses the order of the items in the list

fruits = ["apple", "banana", "orange"]

fruits.append("mango")

print(fruits) # ['apple', 'banana', 'orange', 'mango']

fruits.insert(1,"kiwi")

print(fruits) # ['apple', 'kiwi', 'banana', 'orange', 'mango']

fruits.remove("kiwi")

print(fruits) # ['apple', 'banana', 'orange', 'mango']

fruits.pop(2)

print(fruits) # ['apple', 'banana', 'mango']

fruits.sort()

print(fruits) # ['apple', 'banana', 'mango']

fruits.reverse()

print(fruits) # ['mango', 'banana', 'apple']

Python Tuples

fruits = ("apple", "banana")
more_fruits = ("orange", "mango")

all_fruits = fruits + more_fruits

print(all_fruits) # ('apple', 'banana', 'orange', 'mango')


fruits = ("apple",)

print(fruits * 3) # ('apple', 'apple', 'apple')

fruits = ("apple", "banana", "orange")

print(len(fruits)) # 3

print("banana" in fruits) # True

fruits = ("apple", "banana", "orange", "mango", "lemon")

print(fruits[1:4]) # ('banana', 'orange', 'mango')

fruits = ("apple", "banana", "orange")

fruits[1] = "kiwi" # This will raise a TypeError, as tuples are immutable

Python Dictionary

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print(person['name']) # 'John Doe'

person = {'name': 'John Doe', 'age': 30}
person['gender'] = 'male'

print(person) # {'name': 'John Doe', 'age': 30, 'gender': 'male'}

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}
del person['gender']

print(person) # {'name': 'John Doe', 'age': 30}

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print('name' in person) # True

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print(len(person)) # 3

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print(person.items()) # [('name', 'John Doe'), ('age', 30), ('gender', 'male')]

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print(person.keys()) # ['name', 'age', 'gender']

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}

print(person.values()) # ['John Doe', 30, 'male']

person = {'name': 'John Doe', 'age': 30, 'gender': 'male'}
address = {'city': 'New York', 'state': 'NY'}

person.update(address)

print(person) # {'name': 'John Doe', 'age': 30, 'gender': 'male', 'city': 'New York', 'state': 'NY'}

Python Functions

def print_args(*args, **kwargs):
    print(args)
    print(kwargs)

# Call the function

print_args(1, 2, 3) # prints (1, 2, 3) {}

print_args(a=1, b=2, c=3) # prints () {'a': 1, 'b': 2, 'c': 3}

print_args(1, 2, 3, a=1, b=2, c=3) # prints (1, 2, 3) {'a': 1, 'b': 2, 'c': 3}

def divide(a, b):
    assert b != 0, "Cannot divide by zero"
    return a / b

print(divide(10, 5)) # prints 2.0
print(divide(10, 0)) # raises AssertionError: Cannot divide by zero