Python - Repeat String till K

In Python, you often need to repeat a string to reach a specific length. This is useful for padding, formatting, or creating patterns. Python provides several approaches: string multiplication, while loops, itertools, and list comprehension.

Using String Multiplication

The most efficient method uses string multiplication and slicing to achieve the exact length ?

def repeat_string(text, target_length):
    # Calculate how many complete repetitions we need
    full_repeats = target_length // len(text)
    # Calculate remaining characters needed
    remaining_chars = target_length % len(text)
    
    # Create final string by repeating and adding partial string
    result = text * full_repeats + text[:remaining_chars]
    return result

original = "Hello"
length = 18

repeated = repeat_string(original, length)
print(f"Result: {repeated}")
print(f"Length: {len(repeated)}")

Result: HelloHelloHelloHel
Length: 18

Using While Loop

A while loop keeps adding the string until the target length is reached ?

def repeat_with_loop(text, target_length):
    result = ""
    
    while len(result) < target_length:
        result += text
    
    # Trim to exact length
    return result[:target_length]

original = "ABC"
length = 10

repeated = repeat_with_loop(original, length)
print(f"Result: {repeated}")
print(f"Length: {len(repeated)}")

Result: ABCABCABCA
Length: 10

Using Itertools

The itertools module provides cycle() for infinite repetition and islice() to limit the length ?

import itertools

def repeat_with_itertools(text, target_length):
    # cycle() creates infinite iterator, islice() limits it
    repeated_chars = itertools.islice(itertools.cycle(text), target_length)
    return ''.join(repeated_chars)

original = "XY"
length = 15

repeated = repeat_with_itertools(original, length)
print(f"Result: {repeated}")
print(f"Length: {len(repeated)}")

Result: XYXYXYXYXYXYXYX
Length: 15

Performance Comparison

Practical Example

Creating a progress bar with repeated characters ?

def create_progress_bar(progress_percent, bar_length=20):
    filled_length = int(bar_length * progress_percent / 100)
    bar_char = "?"
    empty_char = "?"
    
    # Repeat characters to create progress bar
    filled_bar = bar_char * filled_length
    empty_bar = empty_char * (bar_length - filled_length)
    
    return f"[{filled_bar}{empty_bar}] {progress_percent}%"

# Test different progress levels
for progress in [25, 50, 75, 100]:
    print(create_progress_bar(progress))

[????????????????????] 25%
[????????????????????] 50%
[????????????????????] 75%
[????????????????????] 100%

Conclusion

String multiplication is the most efficient method for repeating strings to a target length. Use itertools for memory-efficient handling of very large strings, and while loops when you need more control over the repetition process.