CODEWITHSUNDEEP
pythonstring-concatenation
mike
mike

Reputation: 187

is there any way to stop python to concatanate space delimited strings?

Recently we found a couple of bugs in our code based because a developer forgot to add a comma in the middle of a list of strings and python just concatenated the strings. look below:

The intended list was: ["abc", "def"]

Developer wrote: ["abc" "def"]

and we got: ["abcdef"]

now I am concerned over similar mistakes in other part of the code, is this functionality a core part of python? is it possible to disable it?

Upvotes: 1

Views: 111

Answers (1)

unutbu
unutbu

Reputation: 880299

Yes, this is a core part of python:

Multiple adjacent string literals (delimited by whitespace), possibly using different quoting conventions, are allowed, and their meaning is the same as their concatenation. Thus, "hello" 'world' is equivalent to "helloworld".

I don't think there is a way to disable it, short of hacking Python itself.

However, you could use the script below to tokenize your code and warn you when it finds multiple adjacent strings:

import tokenize
import token
import io
import collections


class Token(collections.namedtuple('Token', 'num val start end line')):
    @property
    def name(self):
        return token.tok_name[self.num]

def check(codestr):
    lastname = None
    for tok in tokenize.generate_tokens(io.BytesIO(codestr).readline):
        tok = Token(*tok)
        if lastname == 'STRING' and lastname == tok.name:
            print('ADJACENT STRINGS: {}'.format(tok.line.rstrip()))
        else:
            lastname = tok.name


codestr = '''
'hello'\
'world'

for z in ('foo' 'bar', 'baz'):
    x = ["abc" "def"]
    y = [1, 2, 3]
'''

check(codestr)

yields

ADJACENT STRINGS: 'hello''world'
ADJACENT STRINGS: for z in ('foo' 'bar', 'baz'):
ADJACENT STRINGS:     x = ["abc" "def"]

Upvotes: 8

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