Others have responded, but a note:
> What I want to do is:
```
def my_func(val_1, val_2):
return {
"field_1": val_1 if val_1,
"next_depth": {
"field_2": val_2 if val_2
}
}
```
I am finding this very confusing as to how to generalize this:
How do we know that val_1 belongs to the "top-level" field_1, and val_2 is
in the nested dict with field_2?
Or:
```
def my_func(val_1, val_2):
return {
if val_1 : "field_1": val_1,
"next_depth": {
if val_2: "field_2": val_2
}
}
but this makes it seem like that distinction is hard-coded -- so is the
nested dict is relevant?
> The more core syntax, which should be valid throughout the language,
would be to have statements like `x = y if cond`
we have the
x = y if cond else
expression already -- and an assignment HAS to be assigned to something, so
it seems what you want is:
x = y if cond else None
Maybe the "else None" feels like too much typing, but I prefer the
explicitness myself. (and look in the history of this thread for "null
coalescing" discussion, that _may_ be relevant.
The first of these intuitively reorganizes to `if cond: x = y`
then what do we get for x `if not cond`? it ends up undefined? or set to
whatever value it used to have?
Frankly, I think that's a mistake -- you're going to end up with having to
trap a NameError or do a a hasattr() check later on anyway. It's generally
considered good practice to set a name to None if it isn't defined, rather
than not defining it.
> and `x[y if cond]` ... But the second is not as clear, with a likely
equivalent of `if cond: x[y] else raise Exception`.
assuming x is a dict, then you could do:
d[y if cond else []] = value
It's a hack, but as lists aren't hashable, you get an TypeError, so maybe
that would work for you?
example:
In [16]: key = "Fred"
In [17]: value = "Barnes"
In [18]: d = {}
In [19]: # If the key is Truthy:
In [20]: d[key if key else []] = value
In [21]: d
Out[21]: {'Fred': 'Barnes'}
In [22]: # if the key is Falsey:
In [23]: key = None
In [24]: d[key if key else []] = value
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-24-170a67b9505a> in <module>()
----> 1 d[key if key else []] = value
TypeError: unhashable type: 'list'
-CHB
--
Christopher Barker, PhD
Python Language Consulting
- Teaching
- Scientific Software Development
- Desktop GUI and Web Development
- wxPython, numpy, scipy, Cython
_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/
