处理多个条件函数的大多数pythonic方式

Question

Maybe it is just me, but I seem to come across this problem on almost a daily basis. I've heard in many places that function should be compact and easy to read.

I often have a scenario where I have multiple conditionals which all return different values. Something like.

def conditionals():
    if something1:
        return item1
    if something2:
        return item2
    if something3:
        return item3
         ...

With a lot more conditionals, the function is not compact and certainly not readable. The only way I found to make this better is to make a function specific to each item to return. But then in my code, I feel like I have so many functions for nothing. Anyway, what is the best way to solve this?

Answer 1

If your data is amenable, you could use a dictionary to store the mapping between conditions and actions:

def conditionals(something):
    somethings = {something1: item1, something2: item2, something3: item3}
    try:
        return somethings[something]
    except KeyError:
        return None 

this dictionary could also contain functions that could be called to take an action, based on a condition:

def conditionals(somecondition):
    conditions = {condition1: action1, condition2: action2, condition3: action3}
    try:
       conditions[somecondition]()
    except KeyError:
       print(f"action not found for {somecondition}") 

def action1():
    do_this()

def action2():
    do_that()

def action3():
    do_this()
    do_that()

Answer 2

If your conditions and return values are not too long something like

def f(x):
    return (-x*x      if  x<0  else
            0         if  x<2  else
            (x-2)**3               )

Of course, readability is in the eye of the beholder...