Behavior of exception name binding in Python

exceptions.py

from __future__ import print_function
import sys


def example1():
    try:
        pass   # nothing is raised
    except Exception as e1:
        pass

    print(e1)
    # py2: raises UnboundLocalError
    # py3: raises UnboundLocalError


def example2():
    e2 = 'old local value'
    try:
        pass   # nothing is raised
    except Exception as e2:
        pass

    print(e2)
    # py2: prints 'old local value'
    # py3: prints 'old local value'


e3 = 'global value'
def example3():
    try:
        pass   # nothing is raised
    except Exception as e3:
        pass

    print(e3)
    # py2: raises UnboundLocalError
    # py3: raises UnboundLocalError


def example4():
    try:
        raise ValueError('ve4')
    except Exception as e4:
        pass

    print(e4)
    # py2: prints 've4'
    # py3: raises UnboundLocalError


def example5():
    e5 = 'old local value'
    try:
        raise ValueError('ve5')
    except Exception as e5:
        pass

    print(e5)
    # py2: prints 've5'
    # py3: raises UnboundLocalError


e6 = 'global value'
def example6():
    try:
        raise ValueError('ve6')
    except Exception as e6:
        pass

    print(e6)
    # py2: prints 've6'
    # py3: raises UnboundLocalError


if __name__ == '__main__':
    if len(sys.argv) != 2:
        print('usage: exceptions.py [EXAMPLE_NUMBER]', file=sys.stderr)
        sys.exit(1)
    func_name = 'example{}'.format(sys.argv[1])
    func = globals().get(
        func_name,
        lambda: print('error: `{}` not found'.format(func_name)),
    )
    func()