CODEWITHSUNDEEP
pythonregexpython-2.7
Sanchit Joshi
Sanchit Joshi

Reputation: 45

Regular expression to convert given number in the required format

I am first time using regular expression hence need help with one slightly complex regular expression. I have input list of around 100-150 string object(numbers). 

input = ['90-10-07457', '000480087800784', '001-713-0926', '12-710-8197', '1-345-1715', '9-23-4532', '000200007100272']

Expected output = ['00090-00010-07457', '000480087800784', '00001-00713-00926', '00012-00710-08197', '00001-00345-01715', '00009-00023-04532', '000200007100272']

## I have tried this -

import re
new_list = []
for i in range (0, len(input)):
    new_list.append(re.sub('\d+-\d+-\d+','0000\\1', input[i]))

## problem is with second argument '0000\\1'. I know its wrong but unable to solve
print(new_list)  ## new_list is the expected output.

As you can see, I need to convert string of numbers coming in different formats into 15 digit numbers by adding leading zeros to them.

But there is catch here i.e. some numbers i.e.'000480087800784' are already 15 digits, so should be left unchanged (That's why I cannot use string formatting (.format) option of python) Regex has to be used here, which will modify only required numbers. I have already tried following answers but not been able to solve.

Upvotes: 2

Views: 1264

Answers (2)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626748

Your regex does not work as you used \1 in the replacement, but the regex pattern has no corresponding capturing group. \1 refers to the first capturing group in the pattern.

If you want to try your hand at regex, you may use

re.sub(r'^(\d+)-(\d+)-(\d+)$', lambda x: "{}-{}-{}".format(x.group(1).zfill(5), x.group(2).zfill(5), x.group(3).zfill(5)), input[i])

See the Python demo.

Here, ^(\d+)-(\d+)-(\d+)$ matches a string that starts with 1+ digits, then has -, then 1+ digits, - and again 1+ digits followed by the end of string. There are three capturing groups whose values can be referred to with \1, \2 and \3 backreferences from the replacement pattern. However, since we need to apply .zfill(5) on each captured text, a lambda expression is used as the replacement argument, and the captures are accessed via the match data object group() method.

However, if your strings are already in correct format, you may just split the strings and format as necessary:

for i in range (0, len(input)):
    splits = input[i].split('-')
    if len(splits) == 1:
        new_list.append(input[i])
    else:
        new_list.append("{}-{}-{}".format(splits[0].zfill(5), splits[1].zfill(5), splits[2].zfill(5)))

See another Python demo. Both solutions yield 

['00090-00010-07457', '000480087800784', '00001-00713-00926', '00012-00710-08197', '00001-00345-01715', '00009-00023-04532', '000200007100272']

Upvotes: 1

Asmoox
Asmoox

Reputation: 652

How about analysing the string for numbers and dashes, then adding leading zeros?

input = ['90-10-07457', '000480087800784', '001-713-0926', '12-710-8197', '1-345-1715', '9-23-4532', '000200007100272']
output = []
for inp in input:
    # calculate length of string
    inpLen = len(inp)
    # calculate num of dashes
    inpDashes = inp.count('-')
    # add specific number of leading zeros
    zeros = "0" * (15-(inpLen-inpDashes))
    output.append(zeros + inp)
print (output)

>>> ['00000090-10-07457', '000480087800784', '00000001-713-0926', '00000012-710-8197', '00000001-345-1715', '000000009-23-4532', '000200007100272']

Upvotes: 0

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