/Lib/test/test_print.py

  1"""Test correct operation of the print function.
  2"""
  3
  4# In 2.6, this gives us the behavior we want.  In 3.0, it has
  5#  no function, but it still must parse correctly.
  6from __future__ import print_function
  7
  8import unittest
  9from test import test_support
 10
 11import sys
 12from StringIO import StringIO
 13
 14NotDefined = object()
 15
 16# A dispatch table all 8 combinations of providing
 17#  sep, end, and file
 18# I use this machinery so that I'm not just passing default
 19#  values to print, I'm eiher passing or not passing in the
 20#  arguments
 21dispatch = {
 22    (False, False, False):
 23     lambda args, sep, end, file: print(*args),
 24    (False, False, True):
 25     lambda args, sep, end, file: print(file=file, *args),
 26    (False, True,  False):
 27     lambda args, sep, end, file: print(end=end, *args),
 28    (False, True,  True):
 29     lambda args, sep, end, file: print(end=end, file=file, *args),
 30    (True,  False, False):
 31     lambda args, sep, end, file: print(sep=sep, *args),
 32    (True,  False, True):
 33     lambda args, sep, end, file: print(sep=sep, file=file, *args),
 34    (True,  True,  False):
 35     lambda args, sep, end, file: print(sep=sep, end=end, *args),
 36    (True,  True,  True):
 37     lambda args, sep, end, file: print(sep=sep, end=end, file=file, *args),
 38    }
 39
 40# Class used to test __str__ and print
 41class ClassWith__str__:
 42    def __init__(self, x):
 43        self.x = x
 44    def __str__(self):
 45        return self.x
 46
 47class TestPrint(unittest.TestCase):
 48    def check(self, expected, args,
 49            sep=NotDefined, end=NotDefined, file=NotDefined):
 50        # Capture sys.stdout in a StringIO.  Call print with args,
 51        #  and with sep, end, and file, if they're defined.  Result
 52        #  must match expected.
 53
 54        # Look up the actual function to call, based on if sep, end, and file
 55        #  are defined
 56        fn = dispatch[(sep is not NotDefined,
 57                       end is not NotDefined,
 58                       file is not NotDefined)]
 59
 60        with test_support.captured_stdout() as t:
 61            fn(args, sep, end, file)
 62
 63        self.assertEqual(t.getvalue(), expected)
 64
 65    def test_print(self):
 66        def x(expected, args, sep=NotDefined, end=NotDefined):
 67            # Run the test 2 ways: not using file, and using
 68            #  file directed to a StringIO
 69
 70            self.check(expected, args, sep=sep, end=end)
 71
 72            # When writing to a file, stdout is expected to be empty
 73            o = StringIO()
 74            self.check('', args, sep=sep, end=end, file=o)
 75
 76            # And o will contain the expected output
 77            self.assertEqual(o.getvalue(), expected)
 78
 79        x('\n', ())
 80        x('a\n', ('a',))
 81        x('None\n', (None,))
 82        x('1 2\n', (1, 2))
 83        x('1   2\n', (1, ' ', 2))
 84        x('1*2\n', (1, 2), sep='*')
 85        x('1 s', (1, 's'), end='')
 86        x('a\nb\n', ('a', 'b'), sep='\n')
 87        x('1.01', (1.0, 1), sep='', end='')
 88        x('1*a*1.3+', (1, 'a', 1.3), sep='*', end='+')
 89        x('a\n\nb\n', ('a\n', 'b'), sep='\n')
 90        x('\0+ +\0\n', ('\0', ' ', '\0'), sep='+')
 91
 92        x('a\n b\n', ('a\n', 'b'))
 93        x('a\n b\n', ('a\n', 'b'), sep=None)
 94        x('a\n b\n', ('a\n', 'b'), end=None)
 95        x('a\n b\n', ('a\n', 'b'), sep=None, end=None)
 96
 97        x('*\n', (ClassWith__str__('*'),))
 98        x('abc 1\n', (ClassWith__str__('abc'), 1))
 99
100        # 2.x unicode tests
101        x(u'1 2\n', ('1', u'2'))
102        x(u'u\1234\n', (u'u\1234',))
103        x(u'  abc 1\n', (' ', ClassWith__str__(u'abc'), 1))
104
105        # errors
106        self.assertRaises(TypeError, print, '', sep=3)
107        self.assertRaises(TypeError, print, '', end=3)
108        self.assertRaises(AttributeError, print, '', file='')
109
110    def test_mixed_args(self):
111        # If an unicode arg is passed, sep and end should be unicode, too.
112        class Recorder(object):
113
114            def __init__(self, must_be_unicode):
115                self.buf = []
116                self.force_unicode = must_be_unicode
117
118            def write(self, what):
119                if self.force_unicode and not isinstance(what, unicode):
120                    raise AssertionError("{0!r} is not unicode".format(what))
121                self.buf.append(what)
122
123        buf = Recorder(True)
124        print(u'hi', file=buf)
125        self.assertEqual(u''.join(buf.buf), 'hi\n')
126        del buf.buf[:]
127        print(u'hi', u'nothing', file=buf)
128        self.assertEqual(u''.join(buf.buf), 'hi nothing\n')
129        buf = Recorder(False)
130        print('hi', 'bye', end=u'\n', file=buf)
131        self.assertTrue(isinstance(buf.buf[1], unicode))
132        self.assertTrue(isinstance(buf.buf[3], unicode))
133        del buf.buf[:]
134        print(sep=u'x', file=buf)
135        self.assertTrue(isinstance(buf.buf[-1], unicode))
136
137
138def test_main():
139    test_support.run_unittest(TestPrint)
140
141if __name__ == "__main__":
142    test_main()