ascii_letters in Python

ascii_letters constant in Python is part of the string module and is a predefined string that contains all the lowercase and uppercase ASCII letters. It includes:

• Lowercase letters: abcdefghijklmnopqrstuvwxyz
• Uppercase letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ

It is equivalent to the concatenation of string.ascii_lowercase and string.ascii_uppercase.

Example:

import string

# Accessing ascii_letters
s = string.ascii_letters
print(s) 

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Explanation

• ascii_letters constant combines ascii_lowercase and ascii_uppercase into a single string.
• It contains all lowercase ('a' to 'z') and uppercase ('A' to 'Z') ASCII characters in sequence.

Syntax of ascii_letters

string.ascii_letters

Parameters

• This constant does not take any parameters as it is predefined in the string module.

Return Type

• Returns a string containing all ASCII alphabetic characters, both lowercase and uppercase.

Example 1: Using ascii_letters for validation

If we want to validate whether all characters in a string are ASCII letters. Here's how we can achieve this using the ascii_letters constant:

import string

s = "Hello123"
# Checking if all characters in a string are ASCII letters
res = all(char in string.ascii_letters for char in s)
print(res) 

False

Explanation:

• The string s contains digits ('123'), which are not part of ascii_letters.
• The all() function checks each character, resulting in False since not all characters are ASCII letters.

Example 2: Generating a random string

Sometimes, we need to generate a random string of alphabetic characters for tasks like creating random identifiers. Using ascii_letters, this becomes straightforward:

import string
import random

# Generating a random string of length 8 using ascii_letters
random_string = ''.join(random.choices(string.ascii_letters, k=8))
print(random_string)

yeDgOvur

Explanation:

• random.choices() selects 8 random characters from ascii_letters.
• The join() method combines these characters into a single string, resulting in a random string of alphabetic characters.

Example 3: Counting ASCII letters in a string

We may want to count how many ASCII letters are present in a given string. This is a common task when analyzing text data:

import string

s = "Python3.9 is Awesome!"
# Counting the number of ASCII letters in the string
count = sum(1 for char in s if char in string.ascii_letters)
print(count)  

15

Explanation:

• The generator expression iterates over each character in the string s.
• For each character that is in ascii_letters, the count is incremented, resulting in the total count of ASCII letters.

Example 4: Separating letters from other characters

Consider a situation where we need to extract only the alphabetic characters from a mixed string. ascii_letters simplifies this task:

import string

s = "abc123XYZ!"
# Extracting only ASCII letters from the string
letters_only = ''.join(char for char in s if char in string.ascii_letters)
print(letters_only) 

abcXYZ

Explanation:

• The generator expression filters out characters not in ascii_letters.
• The join() method combines the filtered characters into a new string containing only letters.