Python – Sort given list of strings by part the numeric part of string

When it is required to sort a given list of strings based on the numeric part of the string, we can use regular expressions with the sort() method's key parameter to extract and compare the numeric values.

Example

Below is a demonstration of sorting strings by their numeric parts ?

import re

def extract_numeric_part(string):
    return list(map(int, re.findall(r'\d+', string)))[0]

strings = ["pyt23hon", "fu30n", "lea14rn", 'co00l', 'ob8uje3345t']

print("Original list:")
print(strings)

strings.sort(key=extract_numeric_part)

print("\nSorted list by numeric part:")
print(strings)

Original list:
['pyt23hon', 'fu30n', 'lea14rn', 'co00l', 'ob8uje3345t']

Sorted list by numeric part:
['co00l', 'ob8uje3345t', 'lea14rn', 'pyt23hon', 'fu30n']

How It Works

• The extract_numeric_part() function uses re.findall(r'\d+', string) to find all digit sequences in the string

• It converts the first found numeric sequence to an integer using map(int, ...)[0]

• The sort() method uses this function as the key parameter to determine sort order

• Strings are sorted based on their numeric values: 0, 8, 14, 23, 30

Alternative Approach Using Lambda

You can also use a lambda function for more concise code ?

import re

strings = ["pyt23hon", "fu30n", "lea14rn", 'co00l', 'ob8uje3345t']

sorted_strings = sorted(strings, key=lambda x: int(re.findall(r'\d+', x)[0]))

print("Sorted strings:")
print(sorted_strings)

Sorted strings:
['co00l', 'ob8uje3345t', 'lea14rn', 'pyt23hon', 'fu30n']

Handling Multiple Numbers

If strings contain multiple numbers and you want to sort by the first number ?

import re

strings = ["abc12def34", "xyz5ghi78", "pqr1stu90"]

# Sort by first number found
sorted_strings = sorted(strings, key=lambda x: int(re.findall(r'\d+', x)[0]))

print("Sorted by first number:")
print(sorted_strings)

Sorted by first number:
['pqr1stu90', 'xyz5ghi78', 'abc12def34']

Conclusion

Use re.findall(r'\d+', string) to extract numeric parts from strings and sort them using the key parameter. This approach works efficiently for sorting mixed alphanumeric strings based on their numeric content.