1. For Loop
The for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).
# Syntax
for variable in sequence:
# Code to execute
# Example
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
print(fruit)
2. While Loop
The while loop is used to repeatedly execute a block of code as long as the specified condition is true.
# Syntax
while condition:
# Code to execute
# Example
count = 0
while count < 5:
print(count)
count += 1
3. Nested Loops
Python allows you to nest loops within each other, providing a way to perform more complex iterations.
# Example
for i in range(3):
for j in range(3):
print(i, j)
4. Loop Control Statements
Python provides control statements that allow you to alter the flow of a loop. The break statement terminates the loop, while the continue statement skips the rest of the code in the current iteration.
# Example (break)
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
if fruit == 'banana':
break
print(fruit)
# Example (continue)
numbers = [1, 2, 3, 4, 5]
for num in numbers:
if num % 2 == 0:
continue
print(num)
5. Range Function
The range() function generates a sequence of numbers, commonly used with loops to iterate a specific number of times.
# Syntax
range(start, stop, step)
# Example
for i in range(1, 6, 2):
print(i)
6. Enumerate Function
The enumerate() function is used to iterate over both the values and their indices.
# Example
fruits = ['apple', 'banana', 'cherry']
for index, fruit in enumerate(fruits):
print(index, fruit)
7. List Comprehensions
List comprehensions provide a concise way to create lists. They can also be used to create loops in a single line.
# Example
squares = [x**2 for x in range(5)]
print(squares)
8. Zip Function
The zip() function is used to combine two or more iterables.
# Example
names = ['Alice', 'Bob', 'Charlie']
ages = [25, 30, 22]
for name, age in zip(names, ages):
print(name, age)
9. Else Clause with Loops
In Python, loops can have an else clause which is executed when the loop condition becomes false.
# Example (for loop with else)
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
print(fruit)
else:
print("No more fruits left.")
# Example (while loop with else)
count = 0
while count < 5:
print(count)
count += 1
else:
print("Loop completed.")
10. Pass Statement
The pass statement is a no-operation statement. It’s used when a statement is syntactically required but you want to do nothing.
# Example
for i in range(3):
pass # Placeholder for future code
11. Unpacking in Loops
You can unpack values directly in a loop to simplify code.
# Example
coordinates = [(1, 2), (3, 4), (5, 6)]
for x, y in coordinates:
print(f"X: {x}, Y: {y}")
12. Reversed Function
The reversed() function is used to reverse the order of an iterable.
# Example
numbers = [1, 2, 3, 4, 5]
for num in reversed(numbers):
print(num)
13. Looping Through Dictionaries
Dictionaries can be iterated through their keys, values, or key-value pairs.
# Example (keys)
my_dict = {'a': 1, 'b': 2, 'c': 3}
for key in my_dict:
print(key)
# Example (values)
for value in my_dict.values():
print(value)
# Example (key-value pairs)
for key, value in my_dict.items():
print(key, value)
14. Using Enumerate with a Start Value
You can specify the start value for the enumerate() function.
# Example
fruits = ['apple', 'banana', 'cherry']
for index, fruit in enumerate(fruits, start=1):
print(index, fruit)
15. Looping with Break and Else
Combining break and else can be useful for scenarios where you want to break out of a loop early and still perform some actions.
# Example
for i in range(5):
if i == 3:
print("Breaking loop early.")
break
else:
print("Loop completed.")
