Extract Number before a Character in a String Using Python

Question

I'm trying to extract the number before character "M" in a series of strings. The strings may look like:

"107S33M15H"
"33M100S"
"12M100H33M"

so basically there would be a sets of numbers separated by different characters, and "M" may show up more than once. For the example here, I would like my code to return:

33
33
12,33 #doesn't matter what deliminator to use here

One way I could think of is to split the string by "M", and find items that are pure numbers, but I suspect there are better ways to do it. Thanks a lot for the help.

Wiktor Stribiżew · Accepted Answer · 2016-03-23 00:04:23Z

19

You may use a simple (\d+)M regex (1+ digit(s) followed with M where the digits are captured into a capture group) with re.findall.

See IDEONE demo:

import re
s = "107S33M15H\n33M100S\n12M100H33M"
print(re.findall(r"(\d+)M", s))

And here is a regex demo

answered Mar 23, 2016 at 0:04

Wiktor Stribiżew

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Comments

Camilo · Accepted Answer · 2017-06-20 14:20:18Z

2

You can use rpartition to achieve that job.

s = '107S33M15H'    
prefix = s.rpartition('M')[0]

answered Jun 20, 2017 at 14:20

Camilo

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1 Comment

Jorge Over a year ago

I used this to add a new column to my data frame. This is the code: df['new_col'] = df.old_col.str.rpartition('b')[2] # Where b is the letter to be removed and 2 is the position in the 'rpartition' array of the characters you want in the new column. Thanks for the code. was very useful.

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