Learning Python and a little bit stuck.
I'm trying to set a variable to equal int(stringToInt) or if the string is empty set to None.
I tried to do variable = int(stringToInt) or None but if the string is empty it will error instead of just setting it to None.
Do you know any way around this?
If you want a one-liner like you've attempted, go with this:
variable = int(stringToInt) if stringToInt else None
This will assign variable to int(stringToInt) only if stringToInt is not empty AND is "numeric". If, for example stringToInt is 'mystring', a ValueError will be raised. If stringToInt is empty (''), it will assign variable to None.
To avoid ValueErrors, use a try-except:
try:
variable = int(stringToInt)
except ValueError:
variable = None
stringToInt is 0 then it is not a string. You're right though, that the one-liner will only work for strings, which was what the question was asking about. Also, your proposed solution wouldn't work for empty strings and would raise the same exception OP was receiving. =)
stringToInt will never be None because it's a string, as explained in the question.I think this is the clearest way:
variable = int(stringToInt) if stringToInt.isdigit() else None
variable = int(stringToInt) if stringToInt and stringToInt.isdigit() else None
variable = int(stringToInt) if stringToInt and stringToInt.isdecimal() else None'-1' or strings containing whitespace like ' 1', which int is perfectly capable of parsing. .isdigit() returns false, so you get None. Instead, I'd recommend try-except as in Rob's answer.stringToInt is a string, as explained in the questionUse the fact that it generates an exception:
try:
variable = int(stringToInt)
except ValueError:
variable = None
This has the pleasant side-effect of binding variable to None for other common errors: stringToInt='ZZTop', for example.
None, as calling int() on it raises another exception: "TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'"stringToInt is supposed to be a string, as explained in the question.
this will parse stringToInt to int if it's valid and return original value if it's '' or None
variable = stringToInt and int(stringToInt)
and / or: The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.stringToInt is "", the empty string is returned instead of None.Here are some options:
Catch the exception and handle it:
try:
variable = int(stringToInt)
except ValueError as e:
variable = None
It's not really that exceptional, account for it:
variable = None
if not stringToInt.isdigit():
variable = int(stringtoInt)
all(). if stringToInt.isdigit(): is sufficient.
.isdigit() doesn't work for negative numbers like '-1' or strings containing whitespace like ' 1', which int is perfectly capable of parsing.In addition to the other answers, it can also be a TypeError if stringToInt is None. You can catch it like this:
try:
variable = int(stringToInt)
except (ValueError, TypeError):
variable = None
stringToInt be None? The question says it's a string. I've noticed a lot of people making the same mistake, so is there something about the question that's confusing?stringToInt. In any case it's common situation on stackoverflow when a random question becomes popular due to search engine ranking and people stumbling on edge-cases the original asker didn't consider try to help fellow googlers by adding information they wished they'd found here. Not sure what you're trying to achieve by commenting we're all wrong all over the place.stringToInt." - The question clearly says: "Python String to Int Or None" ... "if the string is empty set to None" ... "if the string is empty it will error". If people have the answer to a different question, they're welcome to post it on a separate question (even post one themselves) and link it here in a comment so that people searching for the same thing in the future can find it. They're also welcome to edit the question to clarify and avoid confusion, if there's anything to clarify.str, bytes, Optional[str | bytes] can be colloquially named a "string", as you can judge from the activity of the people on this page.str. See the docs for example: "Textual data in Python is handled with str objects, or strings." Including bytes too is fine since there's historical precedent from Python 2 and in this context it works the same as str (e.g. int(b'1') → 1). I'm pretty sure people are misinterpreting the question, like maybe "convert string to int, but if it's None, leave it as None".
' 'empty? Any white space?