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"""Test correct operation of the print function.
"""
import unittest
from test import test_support
import sys
import io
from contextlib import contextmanager
NotDefined = object()
# A dispatch table all 8 combinations of providing
# sep, end, and file
# I use this machinery so that I'm not just passing default
# values to print, I'm eiher passing or not passing in the
# arguments
dispatch = {
(False, False, False):
lambda args, sep, end, file: print(*args),
(False, False, True):
lambda args, sep, end, file: print(file=file, *args),
(False, True, False):
lambda args, sep, end, file: print(end=end, *args),
(False, True, True):
lambda args, sep, end, file: print(end=end, file=file, *args),
(True, False, False):
lambda args, sep, end, file: print(sep=sep, *args),
(True, False, True):
lambda args, sep, end, file: print(sep=sep, file=file, *args),
(True, True, False):
lambda args, sep, end, file: print(sep=sep, end=end, *args),
(True, True, True):
lambda args, sep, end, file: print(sep=sep, end=end, file=file, *args),
}
@contextmanager
def stdout_redirected(new_stdout):
save_stdout = sys.stdout
sys.stdout = new_stdout
try:
yield None
finally:
sys.stdout = save_stdout
# Class used to test __str__ and print
class ClassWith__str__:
def __init__(self, x):
self.x = x
def __str__(self):
return self.x
class TestPrint(unittest.TestCase):
def check(self, expected, args, *,
sep=NotDefined, end=NotDefined, file=NotDefined):
# Capture sys.stdout in a StringIO. Call print with args,
# and with sep, end, and file, if they're defined. Result
# must match expected.
# Look up the actual function to call, based on if sep, end, and file
# are defined
fn = dispatch[(sep is not NotDefined,
end is not NotDefined,
file is not NotDefined)]
t = io.StringIO()
with stdout_redirected(t):
fn(args, sep, end, file)
self.assertEqual(t.getvalue(), expected)
def test_print(self):
def x(expected, args, *, sep=NotDefined, end=NotDefined):
# Run the test 2 ways: not using file, and using
# file directed to a StringIO
self.check(expected, args, sep=sep, end=end)
# When writing to a file, stdout is expected to be empty
o = io.StringIO()
self.check('', args, sep=sep, end=end, file=o)
# And o will contain the expected output
self.assertEqual(o.getvalue(), expected)
x('\n', ())
x('a\n', ('a',))
x('None\n', (None,))
x('1 2\n', (1, 2))
x('1*2\n', (1, 2), sep='*')
x('1 s', (1, 's'), end='')
x('a\nb\n', ('a', 'b'), sep='\n')
x('1.01', (1.0, 1), sep='', end='')
x('1*a*1.3+', (1, 'a', 1.3), sep='*', end='+')
x('*\n', (ClassWith__str__('*'),))
def test_main():
test_support.run_unittest(TestPrint)
if __name__ == "__main__":
test_main()
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