CODEWITHSUNDEEP
python
SignalProcessed
SignalProcessed

Reputation: 371

Python: Float needs to return with space after a negative

I can't figure out the correct way to make this happen.

If I have an input of float("- 4"), I want it to return -4.0, regardless of the blank, or whitespace. So this needs to work with other inputs like " - 4", as well. But I don't want this to compromise any other results of the function, so inputs like "4 -", or "5 5" should not be compounded as well.

I wrote a function to try and determine if something is the correct input for my program.

def isNum(num):

   try:
       float(expr)
   except ValueError:
       return False
   return True

It's just the whole input issue above that is frustrating me.

Upvotes: 1

Views: 152

Answers (1)

randomir
randomir

Reputation: 18697

Simply strip the whitespace between - and any digits to the right:

import re
def parse_float(inp):
    return float(re.sub(r'-\s*(\d)', r'-\1', inp))

Example:

>>> parse_float("  -  4  ")
-4.0
>>> parse_float(" 5 ")
5.0

And it'll fail with ValueError for invalid floats:

>>> parse_float("  4 - ")
...
ValueError: invalid literal for float(): 4 - 
>>> parse_float(" 5 5 ")
...
ValueError: invalid literal for float(): 5 5

Upvotes: 2

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