5 ms·
It might work the same depending on your use of it but it's not the same. In that instance L will become a blank list if it is equal to None, zero, or a zero le
by coderdude 14y ago
It might work the same depending on your use of it but it's not the same. In that instance L will become a blank list if it is equal to None, zero, or a zero length string. There are many cases where this wouldn't affect anything, but there can also be instances where that will cause you to define L as a blank list when you really wanted to keep L's value. I think it's always better to be explicit and test for the value(s) you expect.
- chernevik 14y agoAh. These are the little assumptions that keep blowing off my feet. Thanks.
- SoftwareMaven 14y agoIt is these cases that brought the ternary operator to Python: def f(x=None): x if x is not None else []
- iki23 14y agoYes, but why? Actually, it's No, because python culture aims to use one way to do thing, the least surprising one. In this case it's: def f(x=None): if x is None: x = []
- SoftwareMaven 14y agoBecause that "if" is a statement whereas the ternary expression is, well, an expression. There are places expressions can be used that statements can't (eg lambdas) and that x or [] won't work (eg when x is False). That said, people still seem to favor your form as the more Pythonic way. Personally, I think that's just because the ternary expression is relatively new.
- jongraehl 14y agoyou forgot 'return'
- SoftwareMaven 14y agoYeah, I guess my typing went into "lambda mode" since it was a one liner.
- chernevik 14y agoI'm a little confused about this as an assignment to a variable. Is that because of the 'return' omission referred to below? If all function f did was return x, I could see how this works with a 'return' prepended. But if this expression is a line in a larger function, and is intended to reset the value of argument x if no other value is passed in for it, does this really act as an assigment to x? Because I sort of read this expression as evaluating to some value -- the passed value for x, or a [] -- but does this assign that value to the argument x? Or must it be x = [expression]