Python - Splitting numbers and letters into sub-strings with regular expression

Question

I am creating a metric measurement converter. The user is expected to enter in an expression such as 125km (a number followed by a unit abbreviation). For conversion, the numerical value must be split from the abbreviation, producing a result such as [125, 'km']. I have done this with a regular expression, re.split, however it produces unwanted item in the resulting list:

import re
s = '125km'
print(re.split('(\d+)', s))

Output:

['', '125', 'km']

I do not need nor want the beginning ''. How can I simply separate the numerical part of the string from the alphabetical part to produce a list using a regular expression?

@paxdiablo: Sure, but not as simple for m/s^2 (acceleration). — nhahtdh
– nhahtdh, Commented Feb 3, 2015 at 2:57
@Jacob: Unit for energy, J or kg*(m^2)/(s^2), or N*m. It is also equivalent to W*h, which is used to measure electrical consumption (usually kW*h, kilowatt hour). — nhahtdh
– nhahtdh, Commented Feb 3, 2015 at 2:58

Avinash Raj · Accepted Answer · 2015-02-03 02:46:27Z

13

What's wrong with re.findall ?

>>> s = '125km'
>>> re.findall(r'[A-Za-z]+|\d+', s)
['125', 'km']

[A-Za-z]+ matches one or more alphabets. | or \d+ one or more digits.

OR

Use list comprehension.

>>> [i for i in re.split(r'([A-Za-z]+)', s) if i]
['125', 'km']
>>> [i for i in re.split(r'(\d+)', s) if i]
['125', 'km']

answered Feb 3, 2015 at 2:46

Avinash Raj

175k32 gold badges247 silver badges289 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Kikanye Over a year ago

What if the number had decimals, is there a way to handle that case? say 1.25km how can I get ['125', 'km']

Avinash Raj Over a year ago

re.findall(r'[A-Za-z]+|\d+(?:\.\d+)?', s)

Himanshu Gupta · Accepted Answer · 2020-09-17 11:21:28Z

1

Split a string into list of sub-string (number and others)

Using program:

s = "125km1234string"
sub = []
char = ""
num = ""
for letter in s:
    if letter.isdigit():
        if char:
            sub.append(char)
            char = ""
        num += letter
    else:
        if num:
            sub.append(num)
            num = ""
        char += letter
sub.append(char) if char else sub.append(num)
print(sub)

Output

['125', 'km', '1234', 'string']

answered Sep 17, 2020 at 11:21

Himanshu Gupta

771 silver badge6 bronze badges

Collectives™ on Stack Overflow

Python - Splitting numbers and letters into sub-strings with regular expression

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related