Question

what is the best way to match numbers in python

what I trying to do?

I am reading a serial connection, the output is of the range 0 – 1023.
sometimes however I get the following string (they are read as ‘str’):

1023
10?1023
1023

I am matching the output to the alphabet.
the moment I am using:

input = '10?1023'
print sum(int(x) for x in re.findall(r'\d+', input))

as I thought a generator would be quicker than list comprehension.
But matching would give me 1033. Ideally I would like it to return none.

any ideas?, I think I just need to work on the regrep syntax. Is there a way of excluding sum, when using generators?

Answer 1

If I understand correctly, you want to cast a string to an integer, except you want None if it isn’t one.

try:
    y = int(x)
except ValueError:
    y = None

Or if you want to sum all the integers on a single line:

>>> input = """1023
... 10?1023
... 1023
... """
>>> 
>>> sum(int(line) if line.isdigit() else 0 for line in input.splitlines())
2046
>>>