"""
Idiomatic demonstration of re.sub() in Python.
IMPORTANT:
To avoid SyntaxWarning: invalid escape sequence inside docstrings,
we escape backslashes like this:
\\d → literal backslash + d (digit class)
\\s+ → literal backslash + s+ (whitespace class)
Regex patterns themselves MUST remain raw strings:
r"\\d"
r"\\s+"
"""
import re
def mask_digits(text):
"""
Replace every digit with 'X'.
Pattern \\d matches any digit.
"""
return re.sub(r"\d", "X", text)
def normalize_whitespace(text):
"""
Replace any sequence of whitespace with a single space.
Pattern \\s+ matches one or more whitespace characters.
"""
return re.sub(r"\s+", " ", text).strip()
def emphasize_words(text):
"""
Wrap each word in brackets using a function replacement.
Pattern \\w+ matches a word.
"""
def repl(match):
return f"[{match.group(0)}]"
return re.sub(r"\w+", repl, text)
def square_numbers(text):
"""
Square every integer found in the text.
Pattern \\d+ matches one or more digits.
"""
def square(match):
number = int(match.group(0))
return str(number ** 2)
return re.sub(r"\d+", square, text)
# ------------------------------
# Usage
# ------------------------------
sample = "User42 logged in at 10:30.\nNew session started."
masked = mask_digits(sample)
normalized = normalize_whitespace(sample)
emphasized = emphasize_words("Hello Selene, welcome to Python!")
squared = square_numbers("1 2 3 4 5 6 7 8 9")
print("Masked digits:", masked)
print("Normalized whitespace:", normalized)
print("Emphasized words:", emphasized)
print("Squared numbers:", squared)
'''
run:
Masked digits: UserXX logged in at XX:XX.
New session started.
Normalized whitespace: User42 logged in at 10:30. New session started.
Emphasized words: [Hello] [Selene], [welcome] [to] [Python]!
Squared numbers: 1 4 9 16 25 36 49 64 81
'''
