Strings & text
Format, split, join, parse, and clean text — everyday Python string patterns.
Automatically Detect Weak Passwords from Large Password Lists in Python
This Python script identifies weak passwords from a list by checking length, common patterns, sequential characters, and uniform characters, returning those that fail the security checks.
import re
COMMON_PASSWORDS_FILE = "common_passwords.txt"
def is_weak(password):
# Check length
if len(password) < 8:
return True
# Check for common patterns
if password.lower() in {"password", "123456", "qwerty", "letmein", "admin", "welcome"}:
return True
# Check for sequential c…Build a Secure Password Strength Checker in Python
A Python function that evaluates password strength based on length and character diversity, returning Weak, Moderate, or Strong.
import re
def password_strength(password: str) -> str:
score = 0
if len(password) >= 8:
score += 1
if re.search(r'[a-z]', password):
score += 1
if re.search(r'[A-Z]', password):
score += 1
if re.search(r'\d', password):
score += 1
if re.search(r'[!@#$%^&*(),.?":…How to Check Palindrome in Python (Ignore Case and Spaces)
Check whether a string is a palindrome while ignoring case, spaces, and all non-alphanumeric characters using Python's filter and string reversal.
def is_palindrome(text: str) -> bool:
cleaned = ''.join(char.lower() for char in text if char.isalnum())
return cleaned == cleaned[::-1]
if __name__ == "__main__":
test_cases = [
"A man, a plan, a canal: Panama",
"race a car",
"Was it a car or a cat I saw?",
"hello",
…How to Check and Manipulate Strings in Python
Demonstrates core string inspection and transformation methods like case conversion, trimming, splitting, and membership checks on a sample string.
text = " Hello, Python Learners! "
print(f"Original: '{text}'")
print(f"Lowercase: '{text.lower()}'")
print(f"Uppercase: '{text.upper()}'")
print(f"Title case: '{text.title()}'")
print(f"Stripped: '{text.strip()}'")
print(f"Length: {len(text)}")
print(f"Replace: '{text.replace('Python', 'Programming')}'")
print(f"S…How to Check if a String Ends with a File Extension in Python
This code checks whether a filename ends with any of a list of file extensions, handling case insensitivity.
def ends_with_extension(filename, extensions):
"""Check if a filename ends with any of the given extensions."""
lower_name = filename.lower()
return any(lower_name.endswith(ext.lower()) for ext in extensions)
if __name__ == "__main__":
# Test cases
test_files = ["report.pdf", "image.PNG", "script.…How to Check if a String Starts With a Prefix Case-Insensitively in Python
This code defines a function that checks if a string starts with a given prefix, ignoring case, using the lower() method.
def starts_with_case_insensitive(text, prefix):
"""Check if a string starts with a given prefix, ignoring case."""
return text.lower().startswith(prefix.lower())
if __name__ == "__main__":
test_strings = [
("Hello World", "hello"),
("Python Programming", "PYTHON"),
("Data Science"…How to Check if a String is Alphanumeric in Python
Uses the built-in str.isalnum() method to test whether a string contains only letters and numbers.
def is_alphanumeric(s: str) -> bool:
return s.isalnum()
if __name__ == "__main__":
test_cases = ["Hello123", "Hello World", "12345", "", "Hello@World", "Python3"]
for case in test_cases:
result = is_alphanumeric(case)
print(f"{case!r:15} -> {result}")How to Check if a String is Numeric in Python
This code provides a function to determine if a string represents a valid numeric value using Python's built-in float() conversion.
def is_numeric(s):
"""Check if a string represents a valid numeric value."""
try:
float(s)
return True
except (ValueError, TypeError):
return False
if __name__ == "__main__":
test_cases = ["123", "-45.67", "3.14e10", "0x1A", "abc", "12.5.6", " 42 ", ""]
for case in test_c…How to Detect Expired Domains Using Python
Parse a list of domain registration data and compare expiry dates to today to find expired domains.
import datetime
# List of test domains with fake registration and expiry dates
# Format: (domain, registration_date, expiry_date)
test_domains = [
('example.com', '2020-01-15', '2024-01-15'), # Expired
('google.com', '1997-09-15', '2026-09-15'), # Still active
('test-site.org', '2019-06-01', '2023-06-0…How to Detect if a String Contains Only ASCII in Python
This code defines a function that checks whether every character in a given string is an ASCII character (Unicode code point < 128) and demonstrates it with multiple test cases.
def is_ascii_only(text: str) -> bool:
"""Return True if all characters in text are ASCII, False otherwise."""
return all(ord(char) < 128 for char in text)
if __name__ == "__main__":
# Test cases
samples = [
"Hello, world!",
"Café au lait",
"日本語テキスト",
"ASCII only 123",
…How to Validate Text Input in Python: A Simple Text Processor
A Python function that validates a text string by trimming whitespace, then returns a dictionary with character, word, and sentence counts.
def validate_text(text: str) -> dict:
"""Analyze a text string and return basic validation statistics."""
stripped = text.strip()
if not stripped:
return {
"valid": False,
"reason": "Text is empty or only whitespace",
"characters": 0,
"words": 0,
…How to Validate Text Strings in Python
Validate strings with a reusable helper that checks type, length limits, and empty string handling.
def is_valid_text(value, min_length=1, max_length=None, allow_empty=False):
"""
Validate if a value is a string and meets length requirements.
Args:
value: The value to validate
min_length: Minimum allowed length (default 1)
max_length: Maximum allowed length (None = no limit)
…Python String isalpha() Method: Check if String is Alphabetic
This code defines a function that uses Python's str.isalpha() method to determine if a string contains only alphabetic characters, with a demonstration on several test strings.
def is_alphabetic(s):
return s.isalpha()
if __name__ == "__main__":
test_strings = ["Hello", "Hello123", "World!", "Python", ""]
for s in test_strings:
print(f"{s!r}: {is_alphabetic(s)}")Browse by section
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Strings & text — Python code examples
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