In Python, Is An "and" Statement Or All() Faster?

When testing if multiple conditions are True, are and statements or all() faster? For example: if '1234'.isdigit() and '4567'.isdigit() and '7890'.isdigit(): print 'All are di

Solution 1:

ands are faster, there is no list creation and no function call.

In [10]: %timeit '1234'.isdigit() and '4567'.isdigit() and '7890'.isdigit()
1000000 loops, best of 3: 186 ns per loop

In [11]: %timeit all(['1234'.isdigit(), '4567'.isdigit(), '7890'.isdigit()])
1000000 loops, best of 3: 323 ns per loop

 

ands wouldn't even unnecessarily evaluate things:

In [1]: def x():
   ...:     print 'call'
   ...:     returnFalse
   ...:

In [2]: x() and x()
callOut[2]: FalseIn [3]: all([x(), x()])
callcallOut[3]: False

Solution 2:

The second one evaluates all of the conditions, puts those boolean values into a list and then checks to see if they're all true.

The first, on the other hand, just checks them all one-by-one and stops at the first false condition (if there is one). The first one is definitely faster, as Pavel's answer shows.

You could also use a generator, which lets all short-circuit:

all(str.isdigit(s) for s in your_strings)

Solution 3:

If you really want the fastest way to deal with 3 static values, and the dozens of nanoseconds of difference actually matters in your code:

ifTrue:
    print"All are digits!"

Or, even faster:

print"All are digits!"

In any case where the performance matters in the slightest, you will have a large and/or dynamic set of values, and you simply can't do that with and, except by creating an explicit for loop:

value = Truefor s in strings:
    value = value and s.isdigit()
    if not value:
        breakif value:
    print"All are digits!"

And you can immediately see how the and isn't helping things at all:

for s in strings:
    if not s.isdigit():
        breakelse:
    print"All are digits!"

But if you want to do things faster with all, you can use a generator expression (or a map/imap call) instead of a list comprehension, and it's just as fast, and readable, with a large, dynamic sequence as with a small, static one:

ifall((x.isdigit() for x in ('1234', '4567', '7890')):
    print"All are digits!"ifall((x.isdigit() for x in strings):
    print"All are digits!"

If the sequence is very big, and it's possible that some of the values are false, this will be hugely faster than anything involving building a list of all of the True/False values.