For example, I want to check a string and if it is not convertible to integer(with int()), how can I detect that?
2 Answers
Use the .isdigit() method:
>>> '123'.isdigit()
True
>>> '1a23'.isdigit()
False
Quoting the documentation:
Return true if all characters in the string are digits and there is at least one character, false otherwise.
For unicode strings or Python 3 strings, you'll need to use a more precise definition and use the unicode.isdecimal() / str.isdecimal() instead; not all Unicode digits are interpretable as decimal numbers. U+00B2 SUPERSCRIPT 2 is a digit, but not a decimal, for example.
answered Sep 17, 2012 at 19:43
Martijn Pieters
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4 Comments
user1655481
-1 for
a="0x12" a.isdigit()` >>>False
mgilson
I didn't downvote, but
" 1234".isdigit() will return False even though int will happily ignore the space in the front.
Martijn Pieters
@user1655481: that's not a number either, it's a python hex literal.
int('0x12') throws ValueError unless you specify a base.Martijn Pieters
@mgilson: that's kind of the point of the function. It depends on your usecases as to what you need, if
.strip() is needed, etc.You can always try it:
try:
a = int(yourstring)
except ValueError:
print "can't convert"
Note that this method outshines isdigit if you want to know if you can convert a string to a floating point number using float
1 Comment
Ohad
Upvote. It's more pythonic to just try..except :)
'-99'be allowed?