Python string.replace regular expression

Delving into regex specifics and flags

Consider str.replace() as your daily regular coffee, while re.sub() is your fancy Starbucks with all the extra toppings. It takes regular replacements to a next level, unlocking case-insensitive replacements. For repetitive operations, pre-compiling the regex with re.compile() and using re.I flag offer a performance turbo boost!

ch = re.compile(r'coffee', re.IGNORECASE)
new_ch = ch.sub('Starbucks', original_sentence)

# Regular coffee's no match for Starbucks! ☕
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Express regex patterns in raw strings (r"") for a neat and error-free syntax.

Handling files and stringing along lines

When it comes to file manipulation and content replacement, re.sub() is a rock star. Use it within a loop to replace content line-by-line, while your replacement task plays some cool drum-rolls.

with open('file.txt', 'r') as f:
    content = f.readlines()

content = [re.sub(r'<is_despacito>', '<our_new_song>', line) for line in content]

with open('file.txt', 'w') as f:
    f.writelines(content)

# Goodbye Despacito, hello our_new_song 🎸
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The result? An immaculate file chanting our_new_song instead of Despacito.

Substitution with capturing groups and backreferences

Capturing the essence of re.sub() isn't complete without getting a grasp on capturing groups (surround patterns with ()) and backreferences (\1, \2, ...). They let you perform detour operations like "capture this, replace that here".

result = re.sub(r'(\d+)', r'\1 dollars', 'Free money: 2500')
print(result)
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Output: 'Free money: 2500 dollars'
Your coffee is liberated from being '2500,' now it is 2500 dollars! 💸

Implementing complex regex substitutions

You unlock regex wizardry as you utilize quantifiers (+, *, ?), character classes ([a-z]), and more to handle complex substitutions.

# Replace all vowel strings with '*'
result = re.sub(r'[aeiou]+', '*', 'Becomes Night')
print(result)  
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Output: 'Bcms Nght'
Abracadabra — more vowels please! 🧙‍♀️

The safety and efficiency protocol

re.sub() isn't just powerful; it's also safe. When handling user-gen regex patterns, use re.escape() to prevent misunderstanding any special character. It provides a safety regex seatbelt to ensure a smooth and safe ride.