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String methods

Strings come with built-in methods — actions you can run on a string by writing a dot and the method name. They're perfect for cleaning up messy text.

Calling a method

Write the string (or a variable holding one), a dot, the method name, and parentheses:

Python
greeting = "Hello" print(greeting.upper()) # HELLO

Four methods you'll use constantly

Python
text = " Hello, World! " print(text.strip()) # "Hello, World!" (removes surrounding spaces) print(text.lower()) # " hello, world! " print(text.upper()) # " HELLO, WORLD! " print(text.replace("l", "L")) # " HeLLo, WorLd! "
  • .strip() removes whitespace from the start and end (not the middle).
  • .lower() / .upper() change the case of every letter.
  • .replace(old, new) swaps every occurrence of old with new.

Strings are immutable

Methods never change the original string — they return a brand new one. The original stays exactly as it was:

Python
name = "alice" name.upper() # this result is thrown away! print(name) # alice (unchanged) louder = name.upper() print(louder) # ALICE print(name) # alice (still unchanged)

If you want to keep the result, you must store it in a variable (or use it right away). This catches almost every beginner.

Chaining methods

Because each method returns a string, you can call another method on the result:

Python
messy = " Python ROCKS " print(messy.strip().lower()) # "python rocks"

.strip() runs first, then .lower() runs on its result.

Key takeaways

  • Call a method with text.method().
  • .strip(), .lower(), .upper(), and .replace(old, new) are everyday cleaners.
  • Strings are immutable — methods return a new string; store it if you want to keep it.
  • You can chain methods because each one returns a string.