Strip quantities from list using regex

user_18226300 0
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I have an example shopping list:

test_list = "2x 400g beans", "3 x 500 ml choco milk", " 2 chicken breasts"

I want to extract the quantities, not including the units, to get the following result:

quant_list = ['2x 400', '3 x 500', '2']

So far, I have attempted the following:

def strip_quantities(string):
    x = re.search("someregex", string)
    sep = x.start() + 1
    return string.rsplit(string[sep])

quant_list = [strip_quantities(x)[0] for x in test_list]
print(quant_list)

However, I cannot figure out a regular expression, "someregex", that will allow me to split the string (/) at 400/g, 500/ ml, 2/ chicken. The regular expression also needs to ignore (not match) the "2x" in the first list item and "3 x" in the second list item.

I think the expression needs to say "match any letter following a digit or any letter following a digit then whitespace, except when that letter is "x". My best guesses for the expression so far are:

"\d[^x]|\d\s[^x]"

But the output for this is:

['2x 4', '2 ', '2 ']

Not the intended result as stated above. Any help in finding a solution would be greatly appreciated, using regex or alternative method. I've only been learning Python for a few days so any accompanying explanation would be awesome. Thanks!

python regex
3 Answers

Use

\d+(?:\s*x\s*\d+)?

See regex proof.

Python code:

import re
test_list = ["2x 400g beans", "3 x 500 ml choco milk", " 2 chicken breasts"]
for test in test_list:
   match = re.search(r'\d+(?:\s*x\s*\d+)?', test)
   if match:
      print(match.group())

Results: 2x 400, 3 x 500, 2

EXPLANATION

--------------------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  (?:                      group, but do not capture (optional
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    x                        'x'
--------------------------------------------------------------------------------
    \s*                      whitespace (\n, \r, \t, \f, and " ") (0
                             or more times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )?                       end of grouping
user_113298900

You want "match any set of digits that is not followed by optional whitespace and x`. For that, you need a "negative lookahead":

import re
test_list = "2x 400g beans", "3 x 500 ml choco milk", " 2 chicken breasts"

m = r"(\d+)(?! *x)"
for t in test_list:
    print( re.findall( m, t) )

Output:

['400']
['500']
['2']
user_18833160

You can use this regex: ((\d([x\s]?)+)+)

Input: 2x 400g bexfgans", "3 x 500 ml choco milk", " 2 chicken breasts

Output:

2x 400
3 x 500 
2
user_145031050
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