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I want to dynamically concat strings contained in a list dynamically using python but i've run into an error with my logic.

The goal is to concat the strings until an occurence of a string that starts with a digit is found, then isolating this digit string into its own variable and then isolating the remaining strings into a third variable.

For example:

stringList = ["One", "Two", "Three", "456", "Seven", "Eight", "Nine"] resultOne = "OneTwoThree" resultTwo = "456" resultThree = "SevenEightNine"

Here's what i've tried:

stringList = ["One", "Two", "Three", "456", "Seven", "Eight", "Nine"] i = 0 stringOne = "" stringTwo = "" stringThree = "" refStart = 1 for item in stringList: if stringList[i].isdigit() == False: stringOne += stringList[i] i += 1 print(stringOne) elif stringList[i].isdigit == True: stringTwo += stringList[i] i += 1 print(stringTwo) refStart += i else: for stringList[refStart] in stringList: stringThree += stringList[refStart] refStart + 1 += i print(stringThree)

It errors out with the following message:

File "c:\folder\Python\Scripts\test.py", line 19 refStart + 1 += i ^ SyntaxError: 'operator' is an illegal expression for augmented assignment
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  • I don't see "refStart + 1 += i" part of the code Commented Nov 26, 2021 at 14:45
  • oh, my bad. I forgot i had edited it before submitting it Commented Nov 26, 2021 at 17:02

1 Answer 1

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You can use itertools.groupby, a comprehension, and str.join:

stringList = ["One", "Two", "Three", "456", "Seven", "Eight", "Nine"] from itertools import groupby [''.join(g) for k,g in groupby(stringList, lambda x: x[0].isdigit())]

output:

['OneTwoThree', '456', 'SevenEightNine']
how it works:

groupby will group the consecutive values, here I used a test on the first character to detect if it is a digit. So all consecutive strings are joined together.

As a dictionary if the format better suits you:

dict(enumerate(''.join(g) for k,g in groupby(stringList, lambda x: x[0].isdigit())))

output:

{0: 'OneTwoThree', 1: '456', 2: 'SevenEightNine'}

I don't want to join consecutive numbers!

Then you can combine the above with a test on the group identity (True if the string starts with a digit) and use itertools.chain to chain the output:

stringList = ["One", "Two", "Three", "456", "789", "Seven", "Eight", "Nine"] from itertools import groupby, chain list(chain(*(list(g) if k else [''.join(g)] for k,g in groupby(stringList, lambda x: x[0].isdigit()))))

output:

['OneTwoThree', '456', '789', 'SevenEightNine']
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3 Comments

Though i have one more question to add. How could i ignore any occurence of digits after the first one? So i'd have, in that last example: ['OneTwoThree', '456', '789SevenEightNine']
@Matheus do you have numbers repeatedly? Or once in the list? The more details you give on the real data, the easier to give you a good answer ;)
It's hard to say how many can be in the list, all i'm sure of is that the first occurence needs to be isolated. It's a huge 400k lines long dataset

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