import unittest import sys from io import StringIO from test import support 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 either 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), } # 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): """Test correct operation of the print function.""" 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)] with support.captured_stdout() as 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 = 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)) 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('a\n\nb\n', ('a\n', 'b'), sep='\n') x('\0+ +\0\n', ('\0', ' ', '\0'), sep='+') x('a\n b\n', ('a\n', 'b')) x('a\n b\n', ('a\n', 'b'), sep=None) x('a\n b\n', ('a\n', 'b'), end=None) x('a\n b\n', ('a\n', 'b'), sep=None, end=None) x('*\n', (ClassWith__str__('*'),)) x('abc 1\n', (ClassWith__str__('abc'), 1)) # errors self.assertRaises(TypeError, print, '', sep=3) self.assertRaises(TypeError, print, '', end=3) self.assertRaises(AttributeError, print, '', file='') def test_print_flush(self): # operation of the flush flag class filelike: def __init__(self): self.written = '' self.flushed = 0 def write(self, str): self.written += str def flush(self): self.flushed += 1 f = filelike() print(1, file=f, end='', flush=True) print(2, file=f, end='', flush=True) print(3, file=f, flush=False) self.assertEqual(f.written, '123\n') self.assertEqual(f.flushed, 2) # ensure exceptions from flush are passed through class noflush: def write(self, str): pass def flush(self): raise RuntimeError self.assertRaises(RuntimeError, print, 1, file=noflush(), flush=True) class TestPy2MigrationHint(unittest.TestCase): """Test that correct hint is produced analogous to Python3 syntax, if print statement is executed as in Python 2. """ def test_normal_string(self): python2_print_str = 'print "Hello World"' with self.assertRaises(SyntaxError) as context: exec(python2_print_str) self.assertIn('print("Hello World")', str(context.exception)) def test_string_with_soft_space(self): python2_print_str = 'print "Hello World",' with self.assertRaises(SyntaxError) as context: exec(python2_print_str) self.assertIn('print("Hello World", end=" ")', str(context.exception)) def test_string_with_excessive_whitespace(self): python2_print_str = 'print "Hello World", ' with self.assertRaises(SyntaxError) as context: exec(python2_print_str) self.assertIn('print("Hello World", end=" ")', str(context.exception)) def test_string_with_leading_whitespace(self): python2_print_str = '''if 1: print "Hello World" ''' with self.assertRaises(SyntaxError) as context: exec(python2_print_str) self.assertIn('print("Hello World")', str(context.exception)) def test_stream_redirection_hint_for_py2_migration(self): # Test correct hint produced for Py2 redirection syntax with self.assertRaises(TypeError) as context: print >> sys.stderr, "message" self.assertIn('Did you mean "print(, ' 'file=)"?', str(context.exception)) # Test correct hint is produced in the case where RHS implements # __rrshift__ but returns NotImplemented with self.assertRaises(TypeError) as context: print >> 42 self.assertIn('Did you mean "print(, ' 'file=)"?', str(context.exception)) # Test stream redirection hint is specific to print with self.assertRaises(TypeError) as context: max >> sys.stderr self.assertNotIn('Did you mean ', str(context.exception)) # Test stream redirection hint is specific to rshift with self.assertRaises(TypeError) as context: print << sys.stderr self.assertNotIn('Did you mean', str(context.exception)) # Ensure right operand implementing rrshift still works class OverrideRRShift: def __rrshift__(self, lhs): return 42 # Force result independent of LHS self.assertEqual(print >> OverrideRRShift(), 42) if __name__ == "__main__": unittest.main()