3 ms·

For all of the syntax features Python has been adding over the years, this would be a nice enhancement: making the "else None" optional in the ternary if-expres

by cpburns2009 2y ago

For all of the syntax features Python has been adding over the years, this would be a nice enhancement: making the "else None" optional in the ternary if-expression. E.g., spam = eggs if bar # vs spam = eggs if bar else None

genter 2y ago
So if "else None" is omitted, if bar is false, then does spam == None or is it unmodified? The former is what I think you want, but that would be very confusing.
- 333c 2y ago
  Yeah, it would be confusing. In Ruby, this would leave spam unmodified.
  - 8n4vidtmkvmk 2y ago
    That's even more confusing. There's an =, I expect an assignment to happen. Maybe we just leave this one alone.
    - trehalose 2y ago
      Perhaps using a parenthesized assignment expression with the walrus operator would be unambiguous: (spam := eggs) if bar I think that seems reasonable? It would act just the same as it already does with an explicit `else None`, if I'm not mistaken. I don't find it beautiful though.
    - 333c 2y ago
      In Ruby, the `if [condition]` modifier at the end of a line is used for more cases than just assignment. For example, `return if s.blank?` and `raise "invalid" if input.length > 100`. In Ruby, this pattern makes it clear that the statement is only executed if the condition is met. I'm not advocating for this feature to be added to Python, just explaining why it's not confusing in Ruby.
      - mypalmike 2y ago
        Though I used it for 2 years of it as my primary language at work, I never quite got used to Ruby's quirky idioms like this. It just reads badly to me, in terms of quickly understanding code flow, to have statements that start with "raise" or "return" which might not raise or return. Similar to the up-thread comment about assignment.
- entelechy0 2y ago
  [dead]
TwentyPosts 2y ago
Do we really need more syntactic sugar? Frankly, I am still confused why Python is going for a separate syntax for if expressions instead of just making its regular ifs into expressions
- cpfohl 2y ago
  This is literally just a short tutorial helping people get into the cpython codebase. This feedback is off topic. Related to your comment, though: Python has had this syntax for a VERY long time.
- albertzeyer 2y ago
  There is an advantage of having this as syntax, which is a difference in semantics, which you couldn't get if this would just be an expression, namely: x = func1() if something else func2() In this example, only func1() or func2() is being called, but not both.
  - gray_-_wolf 2y ago
    I do not understand why x = if something: func1() else: func2() Would not work. At least that is what I imagine when it is said "make if an expression".
    - __mharrison__ 2y ago
      This doesn't work because the if statement is a statement. Statements don't evaluate to anything in Python, so you can't assign it to x.
      - 8n4vidtmkvmk 2y ago
        Hence "make it an expression"
        otabdeveloper4 2y ago
kstrauser 2y ago
I almost never use None as the second value here. From my POV, that would be new syntax for an unlikely situation.

genter 2y ago

So if "else None" is omitted, if bar is false, then does spam == None or is it unmodified? The former is what I think you want, but that would be very confusing.

333c 2y ago
Yeah, it would be confusing. In Ruby, this would leave spam unmodified.
- 8n4vidtmkvmk 2y ago
  That's even more confusing. There's an =, I expect an assignment to happen. Maybe we just leave this one alone.
  - trehalose 2y ago
    Perhaps using a parenthesized assignment expression with the walrus operator would be unambiguous: (spam := eggs) if bar I think that seems reasonable? It would act just the same as it already does with an explicit `else None`, if I'm not mistaken. I don't find it beautiful though.
  - 333c 2y ago
    In Ruby, the `if [condition]` modifier at the end of a line is used for more cases than just assignment. For example, `return if s.blank?` and `raise "invalid" if input.length > 100`. In Ruby, this pattern makes it clear that the statement is only executed if the condition is met. I'm not advocating for this feature to be added to Python, just explaining why it's not confusing in Ruby.
    - mypalmike 2y ago
      Though I used it for 2 years of it as my primary language at work, I never quite got used to Ruby's quirky idioms like this. It just reads badly to me, in terms of quickly understanding code flow, to have statements that start with "raise" or "return" which might not raise or return. Similar to the up-thread comment about assignment.
entelechy0 2y ago
[dead]

TwentyPosts 2y ago

Do we really need more syntactic sugar? Frankly, I am still confused why Python is going for a separate syntax for if expressions instead of just making its regular ifs into expressions

cpfohl 2y ago
This is literally just a short tutorial helping people get into the cpython codebase. This feedback is off topic. Related to your comment, though: Python has had this syntax for a VERY long time.
albertzeyer 2y ago
There is an advantage of having this as syntax, which is a difference in semantics, which you couldn't get if this would just be an expression, namely: x = func1() if something else func2() In this example, only func1() or func2() is being called, but not both.
- gray_-_wolf 2y ago
  I do not understand why x = if something: func1() else: func2() Would not work. At least that is what I imagine when it is said "make if an expression".
  - __mharrison__ 2y ago
    This doesn't work because the if statement is a statement. Statements don't evaluate to anything in Python, so you can't assign it to x.
    - 8n4vidtmkvmk 2y ago
      Hence "make it an expression"
      - otabdeveloper4 2y ago

kstrauser 2y ago

I almost never use None as the second value here. From my POV, that would be new syntax for an unlikely situation.