Python – Test if String contains any Uppercase character

Last Updated : 10 Jan, 2025

The goal is to check if a given string contains at least one uppercase letter (A-Z).

Using `any()` and `isupper()`

any() function, combined with isdigit(), checks if any character in a string is a digit. It efficiently scans the string and returns True if at least one digit is found.

# Define the input string
s = "abc123"

# Check if the string contains any number
n = any(char.isdigit() for char in s)

# Print the result
if n:
    print("The string contains a number.")
else:
    print("The string does not contain any number.")

Output

The string contains a number.

Explanation:

Check for digits using any() and isdigit(): any() function iterates through each character in the string and isdigit() checks if a character is a digit. If at least one digit is found, any() returns True.
Store the result in a variable: The result is stored in the variable n to indicate whether the string contains any digits.

Using a `for` loop

A for loop can be used to iterate through each character in the string and check if it’s a digit using isdigit(). If a digit is found, the loop can exit early with the result.

# Define the input string
s = "abc123"

# Flag to track if number is found
n = False

# Loop through each character and check if it's a digit
for char in s:
    if char.isdigit():
        n = True
        break

# Print the result
if n:
    print("The string contains a number.")
else:
    print("The string does not contain any number.")

Output

The string contains a number.

Explanation:

Iterate through characters: A for loop goes through each character in the string, checking if it’s a digit using the isdigit() method.
Set flag and exit early: If a digit is found, the flag contains_number is set to True and the loop exits early with a break to avoid unnecessary checks.

Using Regular Expressions

Regular expressions (regex) provide a flexible way to search for patterns in a string. Using re.search(r'\d', text), you can efficiently check if a string contains any digits by looking for the pattern \d (any numeric character).

import re

# Define the input string
s = "abc123"

# Check if the string contains any digit using regex
n = bool(re.search(r'\d', s))

# Print the result
if n:
    print("The string contains a number.")
else:
    print("The string does not contain any number.")

Output

The string contains a number.

Explanation

Search for digits using regex: re.search(r'\d', s) function looks for the pattern \d, which matches any digit, in the string s. If a match is found, it returns a match object; otherwise, it returns None.
Convert to boolean: Result of re.search() is converted to a boolean value using bool(), where True indicates the presence of at least one digit in the string.

Using `filter()` and `isdigit()`

filter() function, combined with isdigit(), can be used to extract all digits from a string. By checking if the filtered result contains any digits, we can determine whether the string includes numeric characters.

# Define the input string
s = "abc123"

# Filter digits and check if any exists
n = bool(list(filter(str.isdigit, s)))

# Print the result
if n:
    print("The string contains a number.")
else:
    print("The string does not contain any number.")

Output

The string contains a number.

Explanation:

Filter digits from the string: filter() function applies str.isdigit to each character in the string, extracting only the numeric characters.
Check for digits: The filtered result is converted to a list and bool() checks if the list is non-empty, indicating the presence of at least one digit.