Question

def gt(nums, n):

    for c in nums:
        if max(nums) > n:
            return True

        elif max(nums) < n:
            return False

        elif not nums:
            return False

for the last elif, it should validate the list of nums whether it is empty or not. But not working for me. Does anyone know what code i can use to check if the list is empty?
Thanks.

Answer 1

You need to check for not nums first. And you don’t need a for loop.

Note that this (like your code) doesn’t explicitly check for max(nums) == n, returning False in this situation (which I think should be the correct behaviour for a function called gt()):

def gt(nums, n):
    if not nums:
        return False
    return max(nums) > n

---

EDIT: Some timings (Python 2.7.3):

>>> import timeit
>>> all = """l = list(range(100))
... rl = list(reversed(range(100)))
... """
>>> tim = all + """def gt(nums, n):
...     if not nums:
...         return False
...     return max(nums) > n"""
>>> gnibbler = all + """def gt(nums, n):
...     return any(x>n for x in nums)"""
>>> burhan = all + """def gt(nums, n):
...   return max(nums) > n if nums else False"""
>>> # Test with the condition being False:
... timeit.timeit(setup=tim, stmt="gt(l, 100)")
3.011574096311698
>>> timeit.timeit(setup=gnibbler, stmt="gt(l, 100)")
8.00847921677337
>>> timeit.timeit(setup=burhan, stmt="gt(l, 100)")
2.9805757305956178
>>> timeit.timeit(setup=tim, stmt="gt(rl, 100)")
2.8600606448831307
>>> timeit.timeit(setup=gnibbler, stmt="gt(l, 100)")
7.997938412127745
>>> timeit.timeit(setup=burhan, stmt="gt(l, 100)")
3.032805185133668
>>> # Now what if the condition is True?
... timeit.timeit(setup=tim, stmt="gt(l, 98)")
2.98623750798793
>>> timeit.timeit(setup=gnibbler, stmt="gt(l, 98)")
8.265056412191534
>>> timeit.timeit(setup=burhan, stmt="gt(l, 98)")
2.9731271156252888
>>> timeit.timeit(setup=tim, stmt="gt(rl, 98)")
2.8777295865334764
>>> timeit.timeit(setup=gnibbler, stmt="gt(rl, 98)")
1.0481696827076092
>>> timeit.timeit(setup=burhan, stmt="gt(rl, 98)")
2.8776150752220246

So Burhan’s and my solution are equivalent in terms of speed (not really surprising since they do exactly the same thing, mine is just a bit more verbose), and gnibbler’s is noticeably faster only if the list is long enough (I’ve removed previous timings where it way always slower when the list only contained ten items), the condition evaluates to True and the search value is reached very early in the list. Otherwise, all the Python-level comparisons will slow it down a lot.