Consider the following code: class Foo: def bar(self) -> Foo: return Foo() This program will actually crash at runtime if you try running it with Python: when the interpreter sees the definition of bar, the definition of Foo is not yet finished. So, since Foo has not yet been added to the global namespace, we … Read more
Some performance measurements, using timeit instead of trying to do it manually with time. First, Apple 2.7.2 64-bit: In [37]: %timeit collections.deque((x for x in xrange(10000000) if x%4 == 0), maxlen=0) 1 loops, best of 3: 1.05 s per loop Now, python.org 3.3.0 64-bit: In [83]: %timeit collections.deque((x for x in range(10000000) if x%4 == … Read more
The recommendation in PEP-8 you are running into is: Always use a def statement instead of an assignment statement that binds a lambda expression directly to a name. Yes: def f(x): return 2*x No: f = lambda x: 2*x The first form means that the name of the resulting function object is specifically ‘f’ instead … Read more
Actually, Guido vetoed the idea: http://bugs.python.org/issue1093 But, as noted in that issue, you can make one pretty easily: from functools import reduce # Valid in Python 2.6+, required in Python 3 import operator reduce(operator.mul, (3, 4, 5), 1)
You should prefer try/except over if/else if that results in speed-ups (for example by preventing extra lookups) cleaner code (fewer lines/easier to read) Often, these go hand-in-hand. speed-ups In the case of trying to find an element in a long list by: try: x = my_list[index] except IndexError: x = ‘NO_ABC’ the try, except is … Read more