Python for Loops

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Python for Loops

A for loop in Python is used to iterate over a sequence such as a list, tuple, set, dictionary, or string. It allows you to execute a block of code once for each element in the sequence.

Unlike traditional for loops in languages like C or Java, Python’s for loop works more like an iterator, automatically moving through each item without requiring an index variable.

Basic for Loop Example

Example: Loop Through a List

cities = ["Delhi", "Mumbai", "Chennai"] for city in cities: print(city)

Delhi Mumbai Chennai

Python automatically assigns each item in the list to the variable city during every iteration.

Note: You do not need to create or manage an index variable manually.

Looping Through a String

Strings are also iterable, meaning you can loop through each character one by one.

Example: Iterating Over Characters

word = "Python" for letter in word: print(letter)

P y t h o n

Each character in the string is accessed sequentially.

The break Statement

The break statement stops the loop immediately, even if there are items left to iterate over.

Example: Stop When a Condition Is Met

numbers = [10, 20, 30, 40, 50] for n in numbers: if n == 30: break print(n)

10 20

Here, the loop exits as soon as the value 30 is found.

break Before Output

Placing break before a print statement prevents the current value from being displayed.

Example

colors = ["red", "green", "blue"] for color in colors: if color == "green": break print(color)

red

The continue Statement

The continue statement skips the current iteration and moves to the next one.

Example: Skip a Specific Value

animals = ["dog", "cat", "cow", "horse"] for animal in animals: if animal == "cat": continue print(animal)

dog cow horse

The loop ignores "cat" and continues with the remaining items.

The range() Function

The range() function is used to repeat a block of code a specific number of times.

Example: Basic range()

for i in range(5): print(i)

0 1 2 3 4

This prints numbers from 0 to 4.

range() with Start Value

You can define where the sequence should begin.

Example

for i in range(3, 8): print(i)

3 4 5 6 7

This generates numbers from 3 to 7.

range() with Step Value

You can also control the increment value.

Example: Custom Step

for i in range(2, 20, 4): print(i)

2 6 10 14 18

This increases the number by 4 each time.

else with for Loop

The else block executes only when the loop completes normally (without hitting break).

Example: Loop Completion

for i in range(4): print(i) else: print("Loop completed successfully")

0 1 2 3 Loop completed successfully

else Skipped When break Is Used

for i in range(6): if i == 4: break print(i) else: print("This will not be printed")

0 1 2 3

Since the loop ends with break, the else block is skipped.

Nested for Loops

A nested loop is a loop inside another loop. The inner loop runs completely for each iteration of the outer loop.

Example: Nested Loop

sizes = ["small", "medium"] items = ["shirt", "jacket"] for size in sizes: for item in items: print(size, item)

small shirt small jacket medium shirt medium jacket

The pass Statement

A for loop cannot be empty. If you need a loop structure without logic (for future implementation), use pass.

Example

for i in range(3): pass

# No output (loop passes successfully)

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