Built-in String Constants

The idea

You need all lowercase letters. Or all digits. Or every punctuation character.

You could type them manually. Or you could let Python hand them to you.

The constants

import string

print(string.ascii_lowercase)   # abcdefghijklmnopqrstuvwxyz
print(string.ascii_uppercase)   # ABCDEFGHIJKLMNOPQRSTUVWXYZ
print(string.ascii_letters)     # abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
print(string.digits)            # 0123456789
print(string.punctuation)       # !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
print(string.whitespace)        # space, tab, newline, and others

These are strings — you can loop over them, check membership, slice them, use them anywhere a string works.

Practical uses

Check if a character is a letter or digit:

import string

char = "R"
print(char in string.ascii_letters)     # True
print(char in string.digits)            # False

Generate a random password:

import string
import random

alphabet = string.ascii_letters + string.digits
password = "".join(random.choice(alphabet) for _ in range(12))
print(password)     # e.g. Xk9mT2rBqL4n

Validate that a string contains only letters:

import string

name = "Raven"
is_valid = all(ch in string.ascii_letters for ch in name)
print(is_valid)     # True

mixed = "Raven123"
print(all(ch in string.ascii_letters for ch in mixed))  # False

Remove punctuation from a string:

import string

text = "Hello, World! How's it going?"
clean = "".join(ch for ch in text if ch not in string.punctuation)
print(clean)    # Hello World Hows it going

Heads up!

• These are constants — strings, not functions. No parentheses.
• ascii_letters = ascii_lowercase + ascii_uppercase
• They only cover ASCII — no accented characters like ă, â, î

What you should understand now

• string.ascii_letters — all letters, upper and lower
• string.digits — 0 through 9
• string.punctuation — all punctuation characters
• Use them with in, loops, and random.choice()