Check a String Contains a Number in Python

1. Python any Function With str.isdigit to Check Whether a String Contains a Number
2. map() Function
3. re.search(r'\d') to Check Whether a String Contains a Number

This article introduces how to check whether a Python string contains a number or not.

Python built-in any function together with str.isdigit will return True if the given string contains a number in it, otherwise, it returns False.

Python regular expression search method with pattern r'\d' could also return True if the given string contains a number.

Python any Function With str.isdigit to Check Whether a String Contains a Number

any function returns True if any element of the given iterable is True, otherwise, it returns False.

str.isdigit() returns True if all the characters in the given string are digits, False otherwise.

any(chr.isdigit() for chr in stringExample)

If stringExample contains at least a number, then the above code returns True because chr.isdigit() for chr in stringExample has at least one True in the iterable.

Working Example

str1 = "python1"
str2 = "nonumber"
str3 = "12345"

print(any(chr.isdigit() for chr in str1))
print(any(chr.isdigit() for chr in str2))
print(any(chr.isdigit() for chr in str3))

Output:

True
False
True

map() Function

Python map(function, iterable) fuction applies function to every element of the given iterable and returns an iterator that yields the above result.

Therefore, we could rewrite the above solution to,

any(map(str.isdigit, stringExample))

Working Example

str1 = "python1"
str2 = "nonumber"
str3 = "12345"

print(any(map(str.isdigit, str1)))
print(any(map(str.isdigit, str2)))
print(any(map(str.isdigit, str3)))

Output:

True
False
True

re.search(r'\d') to Check Whether a String Contains a Number

re.search(r'\d', string) pattern scans the string and returns the match object for the first location that matches the given pattern - \d that means any number between 0 and 9 and returns None if no match is found.

import re

print(re.search(r'\d', "python3.8"))
#output: <re.Match object; span=(6, 7), match='3'>

The match object contains the 2-tuple span that indicates the start and end position of the match, and also the matched content like match = '3'.

bool() function could cast the re.search result from the match object or None to True or False.

Working Example

import re

str1 = "python12"
str2 = "nonumber"
str3 = "12345"

print(bool(re.search(r'\d', str1)))
print(bool(re.search(r'\d', str2)))
print(bool(re.search(r'\d', str3)))

Output:

True
False
True

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