Python – For and While Loops

In Python, loops are used to repeatedly execute a block of code. There are two main types of loops: for loops and while loops. Let’s explore each, including their variations and best practices.

for Loops:

1. Basic for Loop:
   • The basic for loop iterates over a sequence (e.g., a list, tuple, string, or range).
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   for item in sequence:
# Code to execute for each item

2. range() Function with for Loop:
   • The range() function generates a sequence of numbers that can be used with a for loop.
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   for i in range(5):
# Code to execute for each iteration (0 to 4)

3. enumerate() Function:
   • enumerate() is used to iterate over both the indices and values of a sequence.
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   for index, value in enumerate(sequence):
# Code to execute for each index and value

4. zip() Function:
   • zip() combines multiple sequences and iterates over them simultaneously.
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   for item1, item2 in zip(sequence1, sequence2):
# Code to execute for each pair of items


while Loops:

1. Basic while Loop:
   • The basic while loop continues executing as long as a specified condition is True.
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   while condition:
# Code to execute while the condition is True


Loop Control Statements:

1. break Statement:
   • break is used to exit a loop prematurely.
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   for item in sequence:
if condition:
break

2. continue Statement:
   • continue skips the rest of the loop’s code and moves to the next iteration.
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   for item in sequence:
if condition:
continue
# Code to execute for non-matching items


Dos and Don’ts:

Dos:

• Use Descriptive Variable Names: Choose meaningful variable names to enhance code readability.
• Keep Code Inside the Loop Concise: Avoid excessive nesting and keep the code inside the loop focused.
• Use enumerate() and zip() for Multiple Sequences: Simplify code when iterating over multiple sequences.

Don’ts:

• Modify the Sequence Inside a for Loop: Avoid modifying the sequence being iterated over; it can lead to unexpected behavior.
• Use while True Without Proper Exit Conditions: Ensure there is a condition to exit a while True loop to prevent infinite loops.

Best Use Cases:

• for Loops: Ideal for iterating over sequences, such as lists, tuples, and strings.
• while Loops: Useful when the number of iterations is unknown and depends on a condition.
• break and continue: Effective for controlling loop flow and handling specific conditions during iteration.

Loop Cheat Sheet:

This cheat sheet provides an overview of ‘For’ loops, ‘While’ loops, and related concepts in Python, along with dos, don’ts, and best practices for their usage.