The if statement is used for conditional execution:

Syntax:

if <condition>:
       # write code here with indent
elif <condition>:
       # write code here with indent
                ….
else:
       # write code here with indent

Example:

num = input('Enter a Number: ')
num = int(num)

if num <= 0:
    print('Invalid Number')
elif num % 2 == 0:
    print('Even Number')
else:
    print('Odd Number')

print('End of the program')

Match Statements

A match statement takes an expression and compares its value to successive patterns given as one or more case blocks. This is superficially similar to a switch statement in C, Java or JavaScript (and many other languages), but it’s more similar to pattern matching in languages like Rust or Haskell. Only the first pattern that matches gets executed and it can also extract components (sequence elements or object attributes) from the value into variables.

The simplest form compares a subject value against one or more literals:

colour = input("Enter a colour: ")

match colour:
    case "red":
        print("You chose red")
    case "green"|"Green":
        print("You chose green")
    case "blue":
        print("You chose blue")
    case _:
        print("Colour not available")

String indexing and slicing

place = "San Francisco"

# Using for loop without range
for p in reversed(place):
    print(p,end="")
print()

# Using for loop with range
               # from, till, decrement
for p in range(len(place)-1,-1,-1):
    print(place[p],end="")
print()

#Using join
print("".join(reversed(place)))

# Using slicing
print(place[::-1])

Tuple

• A tuple is a collection which is ordered and unchangeable. In Python tuples are written with round brackets.
• You can access tuple items by referring to the index number, inside square brackets.
• Once a tuple is created, you cannot change its values. Tuples are unchangeable.
• You can loop through the tuple items by using a for loop.
• To determine if a specified item is present in a tuple use the in keyword.
• To determine how many items a tuple has, use the len() method.
• Tuples are unchangeable, so you cannot remove items from it, but you can delete the tuple completely.
• It is also possible to use the tuple() constructor to make a tuple

Example:

flowers=('orchids', 'roses', 'lilacs')

print(flowers[0])

print('size of the array is :', len(flowers))

for fl in flowers:
    print(fl)

if 'roses' in flowers:
    print('The flower exists')
else:
    print('The flower doesn\'t exists')

# deletes the array
del flowers

Output:

orchids

size of the array is : 3

orchids

roses

lilacs

The flower exists

Sets

Set in Python is a data structure equivalent to sets in mathematics. It may consist of various elements; the order of elements in a set is undefined. 

You can add and delete elements of a set, you can iterate the elements of the set, you can perform standard operations on sets (union, intersection, difference). Besides that, you can check if an element belongs to a set.

Unlike arrays, where the elements are stored as ordered list, the order of elements in a set is undefined (moreover, the set elements are usually not stored in order of appearance in the set; this allows checking if an element belongs to a set faster than just going through all the elements of the set).

Any immutable data type can be an element of a set: a number, a string, a tuple. 

Mutable (changeable) data types cannot be elements of the set. In particular, list cannot be an element of a set (but tuple can), and another set cannot be an element of a set. 

The requirement of immutability follows from the way how do computers represent sets in memory.

Example

a = {'red', 'yellow', 'blue'}
b = {'red', 'orange', 'green'}

# Add an item to a set, using the add() method:
b.add('pink')

# Add multiple items to a set, using the update() 
# method
a.update({'white', 'pink'})

# Sets are unordered. The items have no index.
for colour in a:
    print(colour)

# A random element is removed from set A
a.pop()



# A specific element is removed from set B
b.remove('orange')


# In order to make a subset, we perform an 
# intersection update
a.intersection_update(b)
print(a)
print(a.issubset(b))

Output:

yellow

red

pink

white

blue

{'pink', 'red'}

True

Dictionary

Functions

A function is a block of code that takes in some data and, either performs some kind of transformation and returns the transformed data, or performs some task on the data, or both.

Functions are useful because they provide a high degree of modularity. Similar code can be easily grouped into functions and you can provide a name to the function that describes what the function is for. 

Functions are the simplest, and, sometimes the most useful, tool for writing modular code.

Syntax:

def name_of_the_function(<arguments>):
    body of the function
    return <value>

Example:

def add(a, b):
    return a + b


def factorial(a):
    if a == 1:
        return 1
    else:
        return a * factorial(a - 1)


addition = add(2, 5)
print(addition)
fact = factorial(7)
print(fact)