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