How to extract numbers from a string that has no spaces into a list

Question

I have an assignment for which my script should be able to receive a string for input (e.g. "c27bdj3jddj45g" ) and extract the numbers into a list (not just the digits, it should be able to detect full numbers).
I am not allowed to use regex at all, only simple methods like split, count and append.
Any ideas? (Using python)

Example for the output needed for the string I gave as an example:
['27','3', '45']

Nothing I have tried so far is worth mentioning here, I am pretty lost on which approach to take here without re.findall, which I cannot use.

Asked By: Rp1013

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Source

Answer 1

s='c27bdj3jddj45g'
lst=[]
for x in s:
    if x.isdigit():
        lst.append(x)
    else:
        lst.append('$')  # here $ is appended as a place holder so that all the numbers can come togetrher

Now, lst becomes :

#['$', '2', '7', '$', '$', '$', '3', '$', '$', '$', '$', '4', '5', '$']

''.join(lst).split('$') becomes:

['', '27', '', '', '3', '', '', '', '45', '']

Finally doing list comprehension to extract the numbers:

[x for x in ''.join(lst).split('$') if x.isdigit()]
['27', '3', '45']

Answered By: Talha Tayyab

Answer 2

You can do this with a for-loop and save the numbers. Then, when you see no digit, append digits and reset the string.

s = 'g38ff11'
prv = ''
res = []
for c in s:
    if c.isdigit():
        prv += c
    else:
        if prv != '': res.append(prv)
        prv = ''
if prv != '': res.append(prv)
print(res)

Output:

['38', '11']

You can also write a lambda to check and append:

s = 'g38ff11'
prv = ''
res = []
append_dgt = lambda prv, res: res.append(prv) if prv!=""  else None
for c in s:
    if c.isdigit():
        prv += c
    else:
        append_dgt(prv,  res)
        prv = ''
append_dgt(prv, res)
print(res)

Answered By: I'mahdi

Answer 3

One way to solve it is to use the groupby from itertools lib:

from itertools import groupby

s = 'c27bdj3jdj45g11'                # last dight is 11
ans = []

for k, g in groupby(s, lambda x: x.isdigit()):
    if k:               #  True if x is digit
        ans.append(''.join(g))

        
ans
['27', '3', '45', '11']

Second solution – even OP has opt out the regex, but this is just for a reference. (to show how much easier to approach this type of puzzle – which should be the way to go)

You could try to use regex – re lib like this (if there’s no restriction!)

s = 'c27bdj3jddj45g'

import re

list(re.findall(r'd+', s))     #  matching one more digits
['27', '3', '45']

# or to get *integer*
list(map(int, re.findall(r'd+', s)))
[27, 3, 45]

Answered By: Daniel Hao

Answer 4

string=’c27bdj3jddj45g’

lst=[]

for i in string:

if i.isdigit():
    lst.append(i)
else:
    lst.append('$')
print([int(i) for i in ''.join(lst).split('$') if i.isdigit()])

Answered By: Diptiranjan Sahoo

How to extract numbers from a string that has no spaces into a list

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