Python convert string to float error with negative numbers

Question

How to convert a negative number stored as string to a float?

Am getting this error on Python 3.6 and don't know how to get over it.

>>> s = '–1123.04'
>>> float(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: '–1123.04'

FWIW, you can use the standard unicodedata module to get the name of each char in string that's behaving mysteriously. Eg, if the string is s do import unicodedata as ud print(*map(ud.name, s), sep=', '). See the module docs for more nifty functions. And of course you can do print(s.encode('unicode-escape')) — PM 2Ring
– PM 2Ring, Commented Jul 23, 2017 at 20:47

BrenBarn · Accepted Answer · 2017-07-23 20:35:04Z

27

Your string contains a unicode en-dash, not an ASCII hyphen. You could replace it:

>>> float('–1123.04'.replace('\U00002013', '-'))
-1123.04

edited Jul 23, 2017 at 20:35

answered Jul 23, 2017 at 20:33

BrenBarn

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3 Comments

idjaw Over a year ago

You can throw this in there if you want to show the difference, if you like.

qwertylpc Over a year ago

can you explain how you see the exact unicode type. I have a slightly different dash and was wondering how to fix my issue

BrenBarn Over a year ago

@qwertylpc: See the comment on the question by Pm 2Ring. You can also use .encode('unicode-escape') to get a representation that will use backslash-escape representations for non-ASCII Unicode characters.

user2589273 · Accepted Answer · 2020-01-21 17:34:01Z

2

For a more generic solution, you can use regular expressions (regex) to replace all non-ascii characters with a hyphen.

import re

s = '–1123.04'

s = re.sub(r'[^\x00-\x7F]+','-', s)

s = float(s)

answered Jan 21, 2020 at 17:34

user2589273

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