python多任务可读性

Question

Simple question - but I cannot seem to find anything via google...

Lets say I have two variables set independently. They should have the same value. Now these two variables find themselves in a new function, ready to be combined.

First I want to make sure they are the same. And then I want to set a third variable (id) to the value of the two (id_1,id_2) to make the code more clear.

id_1=5
id_2=5

# ensure id_1==id_2
assert id_1 == id_2

id=id_1 # option 1
id=id_2 # option 2
id=id_1=id_2 # option 3

What is the correct 'pythonic' way to do this. What is most readable? Or is there a better way to accomplish this (and scale to > 2 initial variables)? Previously I have used (option #1).

Answer 1

def f(*args):
    if args[1:] == args[:-1]: #test all args passed are equal
        id = args[0] #set your 'id' to the first value
    else:
        return None # just as an example
    # do things ...
    return id

>>> f(1,2,3,4)
None
>>> f(1,1,1,1)
1

Answer 2

I would do:

try:
    id = id1 if id1==id2 else int('')
except ValueError as e:
    #fix it or
    raise ValueError('id1 and id2 are different.') from e

and for multiple values:

try:
    id = args[0] if len(set(args))==1 else int('')
except ValueError as e:
    #fix it or
    raise ValueError('id1 and id2 are different.') from e

I usually keep assert for debugging purposes, hence the try statement.

Answer 3

I'd define your other function as taking a list, rather than a bunch of variables you don't really need, then use any to check that they all match. You don't need to check every value against every other value, just check the first one against all the others:

id, *rest = list_of_values # this is Python 3 syntax, on earlier versions use something
                           # like `id, rest = list_of_values[0], list_of_values[1:]`
assert(all(id == other_id for other_id in rest))

# do stuff here with `id`

Note that id isn't really a great name for a variable, since it's also the name of a builtin function (which your code will not be able to use, since its name will be shadowed). If your id s represent some specific kind of objects, you might use a name like foo_id to be more explicit about what its purpose is.