import argparse
import re
ArgumentParser = argparse.ArgumentParser
ArgumentError = argparse.ArgumentError
parser =ArgumentParser()
try:
    parser.add_argument('foo',nargs='1')
except ArgumentError as e:
    print(e)
    assert(re.search(r"nargs (.*) not integer or",str(e)))
parser.add_argument('foo',nargs=1)
group = parser.add_argument_group('g')
try:
    group.add_argument('bar',nargs='**')
except ArgumentError as e:
    print(e)
group.add_argument('bar',nargs='*')
parser.add_argument('baz')
print(parser.format_help())
print(parser.parse_args('foo bar baz'.split()))


m = parser.add_mutually_exclusive_group()
try:
    m.add_argument('-my',nargs='test')
except ArgumentError as e:
    print(e)
    # "nargs 'test' not integer or [None, '?', '*', '+', '...', 'A...']"

#print(parser.format_help())

try:
    parser.add_argument('-w', help='w', nargs='+', metavar=('W1',))
except ArgumentError as e:
    print(e)
except ValueError as e:
    print(e)
    # length of metavar tuple does not match nargs
try:
    group.add_argument('-x', help='x', nargs='*', metavar=('X1', 'X2', 'x3'))
except ArgumentError as e:
    print(e)
except ValueError as e:
    print(e)
m.add_argument('-mz')
try:
    m.add_argument('-y', help='y', nargs=3, metavar=('Y1', 'Y2'))
except ArgumentError as e:
    print(e)
except ValueError as e:
    print(e)
    # length of metavar tuple does not match nargs
m.add_argument('-y', help='y', nargs=3, metavar=('Y1', 'Y2', 'Y3'))
parser.add_argument('-z', help='z', nargs='?', metavar=('Z1', ))

print(parser.format_help())

# test error message from parser._get_nargs_pattern
a = parser.add_argument('--extra',nargs=1)
print(parser.parse_args('foo bar --extra 1'.split()))
a.nargs = 'test'  # change nargs of an established action
try:
    print(parser.parse_args('foo bar --extra 1'.split()))
except ValueError as e:
    print(e)