Proving that Python only evaluates to the first `True` value in an or statement.

or_experiment.py

def first_function(return_value):
    """Returns `return_value`.

    """
    print 'Running FIRST function'
    return return_value


def second_function(return_value):
    """Returns `return_value`.

    """
    print 'Running SECOND function'
    return return_value


def third_function(return_value):
    """Returns `return_value`.

    """
    print 'Running THIRD function'
    return return_value


def main():

    if first_function(True) or second_function(False):
        print 'first clause is True'

    if first_function(False) or second_function(True) or third_function(True):
        print 'second clause is True'

    if first_function(False) or second_function(False) or third_function(True):
        print 'third clause is True'


if __name__ == '__main__':
    main()