在 Python 中执行 for 循环

Question

def search_for_element(L, char):
    for i in L:
        if i == char:
            return True
        else:
            return False

When I run the function, it only outputs one statement on the screen. So why is the for loop only executed once?

Answer 1

return terminates the function, move return False to after the loop:

def search_for_element(L, char):
    for i in L:
        if i == char:
            return True
    return False

Or simply:

def search_for_element(L, char):
    return char in L

Although note the latter is not exactly equivalent, since it also tests identity (not just equality). This will only matter in rather unusual circumstance though, for example numpy.NAN == numpy.NAN is False but numpy.NAN in [numpy.NAN] is True .

So the one-liner alternative would be:

def search_for_element(L, char):
    return any(char == i for i in L)