## Reformatting numbers such as data0000172 to 172 in python

I have a list of strings. Each string has the form of `data0*(\d*)`

if we use a regular expression form.
The following is an example the strings:

data000000, data000003, data0172, data2312, data008212312

I would like to take only the meaningful number portion. All numbers are integers. For example, in the above case, I would like to get another list containing:

0, 3, 172, 2312, 8212312

What would be the best way in the above case?

The following is the solution that I thought:

import re string_list = ["data0000172", ..... ] number_list = [] for string in string_list: match = re.search("data0*(\d+)", string) if match: number_list.append(match.group(1)) else: raise Exception("Wrong format.")

However, the above might be inefficient. Could you suggest a better way for doing this?

If you are *sure* that the strings start with "data", you can just slice the string and convert to integer. Leading zeroes aren't an issue there. Building an integer from a zero-padded digit strings works.

lst = ["data000000", "data000003", "data0172", "data2312", "data008212312"] result = [int(x[4:]) for x in lst]

result:

[0, 3, 172, 2312, 8212312]

or good old replace just in case the prefix can be omitted (but it will be slightly slower):

result = [int(x.replace("data","")) for x in lst]

**Newest 'regex' Questions - Page 5,** how to filter API by URL on Python python regex: either or or both with separator Reformatting numbers such as data0000172 to 172 in python. The numbers module defines a hierarchy of numeric abstract base classes which progressively define more operations. None of the types defined in this module can be instantiated. class numbers.Number¶ The root of the numeric hierarchy. If you just want to check if an argument x is a number, without caring what kind, use isinstance(x, Number).

import re st = 'data0000172' a = float(re.search('data(\d+)',st).group(1)) print(a)

Output:

172.0

This extract the numbers i.e useful part.Apply this to your list.

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In the case where the strings are might not be of the form `data<num>`

and you want the solution to still be valid or if some of the entries are broken for some reason, you can do the following:

import re ll = ['data000000', 'data000003', 'data0172', 'data2312', 'data008212312'] ss = ''.join(ll) res = [int(s) for s in re.findall(r'\d+', ss)] print(res)

The `re.findall`

is applied to the entire list of strings but due to the fact it returns a list of tuples you will get the desired result.

Output:

[0, 3, 172, 2312, 8212312]

**Note**: applying the `re.findall`

to the list without the join will raise an error.

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To me this kind of seemingly simple problem is what Python is all about. Especially if you're coming from a language like C++, where simple text parsing can be a pain in the butt, you'll really appreciate the functionally unit-wise solution that python can give you.

##### Comments

- Why not use int()?
- you can use it. That's not a problem.Based on our need.