How to match text at the start or end of a string in Python?

Checking if a string starts or ends with specific text patterns is a common task in Python programming. The startswith() and endswith() methods provide elegant solutions for pattern matching at string boundaries.

Using startswith() Method

The startswith() method returns True if the string begins with the specified prefix ?

Example

text = "Is USA colder than Australia?"
print(f"Starts with 'Is': {text.startswith('Is')}")

Starts with 'Is': True

Example

filename = "Hello_world.txt"
print(f"Starts with 'Hello': {filename.startswith('Hello')}")

Starts with 'Hello': True

Example

site_url = 'https://www.something.com'
print(f"Starts with 'http:': {site_url.startswith('http:')}")
print(f"Starts with 'https:': {site_url.startswith('https:')}")

Starts with 'http:': False
Starts with 'https:': True

Using endswith() Method

The endswith() method returns True if the string ends with the specified suffix ?

Example

text = "Is USA colder than Australia?"
print(f"Ends with '?': {text.endswith('?')}")

Ends with '?': True

Example

filename = "Hello_world.txt"
print(f"Ends with '.txt': {filename.endswith('.txt')}")

Ends with '.txt': True

Checking Multiple Patterns with Tuples

Both methods accept tuples to check multiple patterns simultaneously. This is especially useful for file extension validation ?

Example

import os
filenames = ['file1.csv', 'document.txt', 'image.png', 'data.csv']

# Check if any files have .csv or .txt extensions
has_target_files = any(name.endswith(('.csv', '.txt')) for name in filenames)
print(f"Has CSV or TXT files: {has_target_files}")

# Get all files with specific extensions
target_files = [name for name in filenames if name.endswith(('.csv', '.txt'))]
print(f"Target files: {target_files}")

Has CSV or TXT files: True
Target files: ['file1.csv', 'document.txt', 'data.csv']

Converting Lists to Tuples

The methods only accept tuples, not lists. If you have a list of patterns, convert it to a tuple ?

Example

# List of patterns (will cause error)
patterns = ['.csv', '.txt']
filenames = ['file1.csv', 'document.txt', 'image.png']

# Convert list to tuple for proper usage
target_files = [name for name in filenames if name.endswith(tuple(patterns))]
print(f"Files matching patterns: {target_files}")

Files matching patterns: ['file1.csv', 'document.txt']

Practical Usage in Conditionals

These methods work well with conditional statements and data processing ?

Example

filenames = ['data.csv', 'report.pdf', 'notes.txt']
extensions = ('.csv', '.txt')

if any(name.endswith(extensions) for name in filenames):
    print("Found text-based files for processing")
    processable_files = [name for name in filenames if name.endswith(extensions)]
    print(f"Processable files: {processable_files}")

Found text-based files for processing
Processable files: ['data.csv', 'notes.txt']

Conclusion

Use startswith() and endswith() for efficient string pattern matching. Pass tuples for multiple pattern checks and convert lists to tuples when needed. These methods integrate seamlessly with conditional logic and data filtering operations.