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Diffstat (limited to 'Lib/test/test_fstring.py')
| -rw-r--r-- | Lib/test/test_fstring.py | 705 |
1 files changed, 705 insertions, 0 deletions
diff --git a/Lib/test/test_fstring.py b/Lib/test/test_fstring.py new file mode 100644 index 0000000000..2ba1b2169f --- /dev/null +++ b/Lib/test/test_fstring.py @@ -0,0 +1,705 @@ +import ast +import types +import decimal +import unittest + +a_global = 'global variable' + +# You could argue that I'm too strict in looking for specific error +# values with assertRaisesRegex, but without it it's way too easy to +# make a syntax error in the test strings. Especially with all of the +# triple quotes, raw strings, backslashes, etc. I think it's a +# worthwhile tradeoff. When I switched to this method, I found many +# examples where I wasn't testing what I thought I was. + +class TestCase(unittest.TestCase): + def assertAllRaise(self, exception_type, regex, error_strings): + for str in error_strings: + with self.subTest(str=str): + with self.assertRaisesRegex(exception_type, regex): + eval(str) + + def test__format__lookup(self): + # Make sure __format__ is looked up on the type, not the instance. + class X: + def __format__(self, spec): + return 'class' + + x = X() + + # Add a bound __format__ method to the 'y' instance, but not + # the 'x' instance. + y = X() + y.__format__ = types.MethodType(lambda self, spec: 'instance', y) + + self.assertEqual(f'{y}', format(y)) + self.assertEqual(f'{y}', 'class') + self.assertEqual(format(x), format(y)) + + # __format__ is not called this way, but still make sure it + # returns what we expect (so we can make sure we're bypassing + # it). + self.assertEqual(x.__format__(''), 'class') + self.assertEqual(y.__format__(''), 'instance') + + # This is how __format__ is actually called. + self.assertEqual(type(x).__format__(x, ''), 'class') + self.assertEqual(type(y).__format__(y, ''), 'class') + + def test_ast(self): + # Inspired by http://bugs.python.org/issue24975 + class X: + def __init__(self): + self.called = False + def __call__(self): + self.called = True + return 4 + x = X() + expr = """ +a = 10 +f'{a * x()}'""" + t = ast.parse(expr) + c = compile(t, '', 'exec') + + # Make sure x was not called. + self.assertFalse(x.called) + + # Actually run the code. + exec(c) + + # Make sure x was called. + self.assertTrue(x.called) + + def test_literal_eval(self): + # With no expressions, an f-string is okay. + self.assertEqual(ast.literal_eval("f'x'"), 'x') + self.assertEqual(ast.literal_eval("f'x' 'y'"), 'xy') + + # But this should raise an error. + with self.assertRaisesRegex(ValueError, 'malformed node or string'): + ast.literal_eval("f'x{3}'") + + # As should this, which uses a different ast node + with self.assertRaisesRegex(ValueError, 'malformed node or string'): + ast.literal_eval("f'{3}'") + + def test_ast_compile_time_concat(self): + x = [''] + + expr = """x[0] = 'foo' f'{3}'""" + t = ast.parse(expr) + c = compile(t, '', 'exec') + exec(c) + self.assertEqual(x[0], 'foo3') + + def test_literal(self): + self.assertEqual(f'', '') + self.assertEqual(f'a', 'a') + self.assertEqual(f' ', ' ') + + def test_unterminated_string(self): + self.assertAllRaise(SyntaxError, 'f-string: unterminated string', + [r"""f'{"x'""", + r"""f'{"x}'""", + r"""f'{("x'""", + r"""f'{("x}'""", + ]) + + def test_mismatched_parens(self): + self.assertAllRaise(SyntaxError, 'f-string: mismatched', + ["f'{((}'", + ]) + + def test_double_braces(self): + self.assertEqual(f'{{', '{') + self.assertEqual(f'a{{', 'a{') + self.assertEqual(f'{{b', '{b') + self.assertEqual(f'a{{b', 'a{b') + self.assertEqual(f'}}', '}') + self.assertEqual(f'a}}', 'a}') + self.assertEqual(f'}}b', '}b') + self.assertEqual(f'a}}b', 'a}b') + + self.assertEqual(f'{{{10}', '{10') + self.assertEqual(f'}}{10}', '}10') + self.assertEqual(f'}}{{{10}', '}{10') + self.assertEqual(f'}}a{{{10}', '}a{10') + + self.assertEqual(f'{10}{{', '10{') + self.assertEqual(f'{10}}}', '10}') + self.assertEqual(f'{10}}}{{', '10}{') + self.assertEqual(f'{10}}}a{{' '}', '10}a{}') + + # Inside of strings, don't interpret doubled brackets. + self.assertEqual(f'{"{{}}"}', '{{}}') + + self.assertAllRaise(TypeError, 'unhashable type', + ["f'{ {{}} }'", # dict in a set + ]) + + def test_compile_time_concat(self): + x = 'def' + self.assertEqual('abc' f'## {x}ghi', 'abc## defghi') + self.assertEqual('abc' f'{x}' 'ghi', 'abcdefghi') + self.assertEqual('abc' f'{x}' 'gh' f'i{x:4}', 'abcdefghidef ') + self.assertEqual('{x}' f'{x}', '{x}def') + self.assertEqual('{x' f'{x}', '{xdef') + self.assertEqual('{x}' f'{x}', '{x}def') + self.assertEqual('{{x}}' f'{x}', '{{x}}def') + self.assertEqual('{{x' f'{x}', '{{xdef') + self.assertEqual('x}}' f'{x}', 'x}}def') + self.assertEqual(f'{x}' 'x}}', 'defx}}') + self.assertEqual(f'{x}' '', 'def') + self.assertEqual('' f'{x}' '', 'def') + self.assertEqual('' f'{x}', 'def') + self.assertEqual(f'{x}' '2', 'def2') + self.assertEqual('1' f'{x}' '2', '1def2') + self.assertEqual('1' f'{x}', '1def') + self.assertEqual(f'{x}' f'-{x}', 'def-def') + self.assertEqual('' f'', '') + self.assertEqual('' f'' '', '') + self.assertEqual('' f'' '' f'', '') + self.assertEqual(f'', '') + self.assertEqual(f'' '', '') + self.assertEqual(f'' '' f'', '') + self.assertEqual(f'' '' f'' '', '') + + self.assertAllRaise(SyntaxError, "f-string: expecting '}'", + ["f'{3' f'}'", # can't concat to get a valid f-string + ]) + + def test_comments(self): + # These aren't comments, since they're in strings. + d = {'#': 'hash'} + self.assertEqual(f'{"#"}', '#') + self.assertEqual(f'{d["#"]}', 'hash') + + self.assertAllRaise(SyntaxError, "f-string cannot include '#'", + ["f'{1#}'", # error because the expression becomes "(1#)" + "f'{3(#)}'", + ]) + + def test_many_expressions(self): + # Create a string with many expressions in it. Note that + # because we have a space in here as a literal, we're actually + # going to use twice as many ast nodes: one for each literal + # plus one for each expression. + def build_fstr(n, extra=''): + return "f'" + ('{x} ' * n) + extra + "'" + + x = 'X' + width = 1 + + # Test around 256. + for i in range(250, 260): + self.assertEqual(eval(build_fstr(i)), (x+' ')*i) + + # Test concatenating 2 largs fstrings. + self.assertEqual(eval(build_fstr(255)*256), (x+' ')*(255*256)) + + s = build_fstr(253, '{x:{width}} ') + self.assertEqual(eval(s), (x+' ')*254) + + # Test lots of expressions and constants, concatenated. + s = "f'{1}' 'x' 'y'" * 1024 + self.assertEqual(eval(s), '1xy' * 1024) + + def test_format_specifier_expressions(self): + width = 10 + precision = 4 + value = decimal.Decimal('12.34567') + self.assertEqual(f'result: {value:{width}.{precision}}', 'result: 12.35') + self.assertEqual(f'result: {value:{width!r}.{precision}}', 'result: 12.35') + self.assertEqual(f'result: {value:{width:0}.{precision:1}}', 'result: 12.35') + self.assertEqual(f'result: {value:{1}{0:0}.{precision:1}}', 'result: 12.35') + self.assertEqual(f'result: {value:{ 1}{ 0:0}.{ precision:1}}', 'result: 12.35') + self.assertEqual(f'{10:#{1}0x}', ' 0xa') + self.assertEqual(f'{10:{"#"}1{0}{"x"}}', ' 0xa') + self.assertEqual(f'{-10:-{"#"}1{0}x}', ' -0xa') + self.assertEqual(f'{-10:{"-"}#{1}0{"x"}}', ' -0xa') + self.assertEqual(f'{10:#{3 != {4:5} and width}x}', ' 0xa') + + self.assertAllRaise(SyntaxError, "f-string: expecting '}'", + ["""f'{"s"!r{":10"}}'""", + + # This looks like a nested format spec. + ]) + + self.assertAllRaise(SyntaxError, "invalid syntax", + [# Invalid syntax inside a nested spec. + "f'{4:{/5}}'", + ]) + + self.assertAllRaise(SyntaxError, "f-string: expressions nested too deeply", + [# Can't nest format specifiers. + "f'result: {value:{width:{0}}.{precision:1}}'", + ]) + + self.assertAllRaise(SyntaxError, 'f-string: invalid conversion character', + [# No expansion inside conversion or for + # the : or ! itself. + """f'{"s"!{"r"}}'""", + ]) + + def test_side_effect_order(self): + class X: + def __init__(self): + self.i = 0 + def __format__(self, spec): + self.i += 1 + return str(self.i) + + x = X() + self.assertEqual(f'{x} {x}', '1 2') + + def test_missing_expression(self): + self.assertAllRaise(SyntaxError, 'f-string: empty expression not allowed', + ["f'{}'", + "f'{ }'" + "f' {} '", + "f'{!r}'", + "f'{ !r}'", + "f'{10:{ }}'", + "f' { } '", + + # Catch the empty expression before the + # invalid conversion. + "f'{!x}'", + "f'{ !xr}'", + "f'{!x:}'", + "f'{!x:a}'", + "f'{ !xr:}'", + "f'{ !xr:a}'", + + "f'{!}'", + "f'{:}'", + + # We find the empty expression before the + # missing closing brace. + "f'{!'", + "f'{!s:'", + "f'{:'", + "f'{:x'", + ]) + + def test_parens_in_expressions(self): + self.assertEqual(f'{3,}', '(3,)') + + # Add these because when an expression is evaluated, parens + # are added around it. But we shouldn't go from an invalid + # expression to a valid one. The added parens are just + # supposed to allow whitespace (including newlines). + self.assertAllRaise(SyntaxError, 'invalid syntax', + ["f'{,}'", + "f'{,}'", # this is (,), which is an error + ]) + + self.assertAllRaise(SyntaxError, "f-string: expecting '}'", + ["f'{3)+(4}'", + ]) + + self.assertAllRaise(SyntaxError, 'EOL while scanning string literal', + ["f'{\n}'", + ]) + + def test_no_backslashes(self): + # See issue 27921 + + # These should work, but currently don't + self.assertAllRaise(SyntaxError, 'backslashes not allowed', + [r"f'\t'", + r"f'{2}\t'", + r"f'{2}\t{3}'", + r"f'\t{3}'", + + r"f'\N{GREEK CAPITAL LETTER DELTA}'", + r"f'{2}\N{GREEK CAPITAL LETTER DELTA}'", + r"f'{2}\N{GREEK CAPITAL LETTER DELTA}{3}'", + r"f'\N{GREEK CAPITAL LETTER DELTA}{3}'", + + r"f'\u0394'", + r"f'{2}\u0394'", + r"f'{2}\u0394{3}'", + r"f'\u0394{3}'", + + r"f'\U00000394'", + r"f'{2}\U00000394'", + r"f'{2}\U00000394{3}'", + r"f'\U00000394{3}'", + + r"f'\x20'", + r"f'{2}\x20'", + r"f'{2}\x20{3}'", + r"f'\x20{3}'", + + r"f'2\x20'", + r"f'2\x203'", + r"f'2\x203'", + ]) + + # And these don't work now, and shouldn't work in the future. + self.assertAllRaise(SyntaxError, 'backslashes not allowed', + [r"f'{\'a\'}'", + r"f'{\t3}'", + ]) + + # add this when backslashes are allowed again. see issue 27921 + # these test will be needed because unicode names will be parsed + # differently once backslashes are allowed inside expressions + ## def test_misformed_unicode_character_name(self): + ## self.assertAllRaise(SyntaxError, 'xx', + ## [r"f'\N'", + ## [r"f'\N{'", + ## [r"f'\N{GREEK CAPITAL LETTER DELTA'", + ## ]) + + def test_newlines_in_expressions(self): + self.assertEqual(f'{0}', '0') + self.assertEqual(rf'''{3+ +4}''', '7') + + def test_lambda(self): + x = 5 + self.assertEqual(f'{(lambda y:x*y)("8")!r}', "'88888'") + self.assertEqual(f'{(lambda y:x*y)("8")!r:10}', "'88888' ") + self.assertEqual(f'{(lambda y:x*y)("8"):10}', "88888 ") + + # lambda doesn't work without parens, because the colon + # makes the parser think it's a format_spec + self.assertAllRaise(SyntaxError, 'unexpected EOF while parsing', + ["f'{lambda x:x}'", + ]) + + def test_yield(self): + # Not terribly useful, but make sure the yield turns + # a function into a generator + def fn(y): + f'y:{yield y*2}' + + g = fn(4) + self.assertEqual(next(g), 8) + + def test_yield_send(self): + def fn(x): + yield f'x:{yield (lambda i: x * i)}' + + g = fn(10) + the_lambda = next(g) + self.assertEqual(the_lambda(4), 40) + self.assertEqual(g.send('string'), 'x:string') + + def test_expressions_with_triple_quoted_strings(self): + self.assertEqual(f"{'''x'''}", 'x') + self.assertEqual(f"{'''eric's'''}", "eric's") + + # Test concatenation within an expression + self.assertEqual(f'{"x" """eric"s""" "y"}', 'xeric"sy') + self.assertEqual(f'{"x" """eric"s"""}', 'xeric"s') + self.assertEqual(f'{"""eric"s""" "y"}', 'eric"sy') + self.assertEqual(f'{"""x""" """eric"s""" "y"}', 'xeric"sy') + self.assertEqual(f'{"""x""" """eric"s""" """y"""}', 'xeric"sy') + self.assertEqual(f'{r"""x""" """eric"s""" """y"""}', 'xeric"sy') + + def test_multiple_vars(self): + x = 98 + y = 'abc' + self.assertEqual(f'{x}{y}', '98abc') + + self.assertEqual(f'X{x}{y}', 'X98abc') + self.assertEqual(f'{x}X{y}', '98Xabc') + self.assertEqual(f'{x}{y}X', '98abcX') + + self.assertEqual(f'X{x}Y{y}', 'X98Yabc') + self.assertEqual(f'X{x}{y}Y', 'X98abcY') + self.assertEqual(f'{x}X{y}Y', '98XabcY') + + self.assertEqual(f'X{x}Y{y}Z', 'X98YabcZ') + + def test_closure(self): + def outer(x): + def inner(): + return f'x:{x}' + return inner + + self.assertEqual(outer('987')(), 'x:987') + self.assertEqual(outer(7)(), 'x:7') + + def test_arguments(self): + y = 2 + def f(x, width): + return f'x={x*y:{width}}' + + self.assertEqual(f('foo', 10), 'x=foofoo ') + x = 'bar' + self.assertEqual(f(10, 10), 'x= 20') + + def test_locals(self): + value = 123 + self.assertEqual(f'v:{value}', 'v:123') + + def test_missing_variable(self): + with self.assertRaises(NameError): + f'v:{value}' + + def test_missing_format_spec(self): + class O: + def __format__(self, spec): + if not spec: + return '*' + return spec + + self.assertEqual(f'{O():x}', 'x') + self.assertEqual(f'{O()}', '*') + self.assertEqual(f'{O():}', '*') + + self.assertEqual(f'{3:}', '3') + self.assertEqual(f'{3!s:}', '3') + + def test_global(self): + self.assertEqual(f'g:{a_global}', 'g:global variable') + self.assertEqual(f'g:{a_global!r}', "g:'global variable'") + + a_local = 'local variable' + self.assertEqual(f'g:{a_global} l:{a_local}', + 'g:global variable l:local variable') + self.assertEqual(f'g:{a_global!r}', + "g:'global variable'") + self.assertEqual(f'g:{a_global} l:{a_local!r}', + "g:global variable l:'local variable'") + + self.assertIn("module 'unittest' from", f'{unittest}') + + def test_shadowed_global(self): + a_global = 'really a local' + self.assertEqual(f'g:{a_global}', 'g:really a local') + self.assertEqual(f'g:{a_global!r}', "g:'really a local'") + + a_local = 'local variable' + self.assertEqual(f'g:{a_global} l:{a_local}', + 'g:really a local l:local variable') + self.assertEqual(f'g:{a_global!r}', + "g:'really a local'") + self.assertEqual(f'g:{a_global} l:{a_local!r}', + "g:really a local l:'local variable'") + + def test_call(self): + def foo(x): + return 'x=' + str(x) + + self.assertEqual(f'{foo(10)}', 'x=10') + + def test_nested_fstrings(self): + y = 5 + self.assertEqual(f'{f"{0}"*3}', '000') + self.assertEqual(f'{f"{y}"*3}', '555') + + def test_invalid_string_prefixes(self): + self.assertAllRaise(SyntaxError, 'unexpected EOF while parsing', + ["fu''", + "uf''", + "Fu''", + "fU''", + "Uf''", + "uF''", + "ufr''", + "urf''", + "fur''", + "fru''", + "rfu''", + "ruf''", + "FUR''", + "Fur''", + ]) + + def test_leading_trailing_spaces(self): + self.assertEqual(f'{ 3}', '3') + self.assertEqual(f'{ 3}', '3') + self.assertEqual(f'{3 }', '3') + self.assertEqual(f'{3 }', '3') + + self.assertEqual(f'expr={ {x: y for x, y in [(1, 2), ]}}', + 'expr={1: 2}') + self.assertEqual(f'expr={ {x: y for x, y in [(1, 2), ]} }', + 'expr={1: 2}') + + def test_not_equal(self): + # There's a special test for this because there's a special + # case in the f-string parser to look for != as not ending an + # expression. Normally it would, while looking for !s or !r. + + self.assertEqual(f'{3!=4}', 'True') + self.assertEqual(f'{3!=4:}', 'True') + self.assertEqual(f'{3!=4!s}', 'True') + self.assertEqual(f'{3!=4!s:.3}', 'Tru') + + def test_conversions(self): + self.assertEqual(f'{3.14:10.10}', ' 3.14') + self.assertEqual(f'{3.14!s:10.10}', '3.14 ') + self.assertEqual(f'{3.14!r:10.10}', '3.14 ') + self.assertEqual(f'{3.14!a:10.10}', '3.14 ') + + self.assertEqual(f'{"a"}', 'a') + self.assertEqual(f'{"a"!r}', "'a'") + self.assertEqual(f'{"a"!a}', "'a'") + + # Not a conversion. + self.assertEqual(f'{"a!r"}', "a!r") + + # Not a conversion, but show that ! is allowed in a format spec. + self.assertEqual(f'{3.14:!<10.10}', '3.14!!!!!!') + + self.assertAllRaise(SyntaxError, 'f-string: invalid conversion character', + ["f'{3!g}'", + "f'{3!A}'", + "f'{3!A}'", + "f'{3!A}'", + "f'{3!!}'", + "f'{3!:}'", + "f'{3! s}'", # no space before conversion char + ]) + + self.assertAllRaise(SyntaxError, "f-string: expecting '}'", + ["f'{x!s{y}}'", + "f'{3!ss}'", + "f'{3!ss:}'", + "f'{3!ss:s}'", + ]) + + def test_assignment(self): + self.assertAllRaise(SyntaxError, 'invalid syntax', + ["f'' = 3", + "f'{0}' = x", + "f'{x}' = x", + ]) + + def test_del(self): + self.assertAllRaise(SyntaxError, 'invalid syntax', + ["del f''", + "del '' f''", + ]) + + def test_mismatched_braces(self): + self.assertAllRaise(SyntaxError, "f-string: single '}' is not allowed", + ["f'{{}'", + "f'{{}}}'", + "f'}'", + "f'x}'", + "f'x}x'", + + # Can't have { or } in a format spec. + "f'{3:}>10}'", + "f'{3:}}>10}'", + ]) + + self.assertAllRaise(SyntaxError, "f-string: expecting '}'", + ["f'{3:{{>10}'", + "f'{3'", + "f'{3!'", + "f'{3:'", + "f'{3!s'", + "f'{3!s:'", + "f'{3!s:3'", + "f'x{'", + "f'x{x'", + "f'{3:s'", + "f'{{{'", + "f'{{}}{'", + "f'{'", + ]) + + # But these are just normal strings. + self.assertEqual(f'{"{"}', '{') + self.assertEqual(f'{"}"}', '}') + self.assertEqual(f'{3:{"}"}>10}', '}}}}}}}}}3') + self.assertEqual(f'{2:{"{"}>10}', '{{{{{{{{{2') + + def test_if_conditional(self): + # There's special logic in compile.c to test if the + # conditional for an if (and while) are constants. Exercise + # that code. + + def test_fstring(x, expected): + flag = 0 + if f'{x}': + flag = 1 + else: + flag = 2 + self.assertEqual(flag, expected) + + def test_concat_empty(x, expected): + flag = 0 + if '' f'{x}': + flag = 1 + else: + flag = 2 + self.assertEqual(flag, expected) + + def test_concat_non_empty(x, expected): + flag = 0 + if ' ' f'{x}': + flag = 1 + else: + flag = 2 + self.assertEqual(flag, expected) + + test_fstring('', 2) + test_fstring(' ', 1) + + test_concat_empty('', 2) + test_concat_empty(' ', 1) + + test_concat_non_empty('', 1) + test_concat_non_empty(' ', 1) + + def test_empty_format_specifier(self): + x = 'test' + self.assertEqual(f'{x}', 'test') + self.assertEqual(f'{x:}', 'test') + self.assertEqual(f'{x!s:}', 'test') + self.assertEqual(f'{x!r:}', "'test'") + + def test_str_format_differences(self): + d = {'a': 'string', + 0: 'integer', + } + a = 0 + self.assertEqual(f'{d[0]}', 'integer') + self.assertEqual(f'{d["a"]}', 'string') + self.assertEqual(f'{d[a]}', 'integer') + self.assertEqual('{d[a]}'.format(d=d), 'string') + self.assertEqual('{d[0]}'.format(d=d), 'integer') + + def test_invalid_expressions(self): + self.assertAllRaise(SyntaxError, 'invalid syntax', + [r"f'{a[4)}'", + r"f'{a(4]}'", + ]) + + def test_errors(self): + # see issue 26287 + self.assertAllRaise(TypeError, 'non-empty', + [r"f'{(lambda: 0):x}'", + r"f'{(0,):x}'", + ]) + self.assertAllRaise(ValueError, 'Unknown format code', + [r"f'{1000:j}'", + r"f'{1000:j}'", + ]) + + def test_loop(self): + for i in range(1000): + self.assertEqual(f'i:{i}', 'i:' + str(i)) + + def test_dict(self): + d = {'"': 'dquote', + "'": 'squote', + 'foo': 'bar', + } + self.assertEqual(f'''{d["'"]}''', 'squote') + self.assertEqual(f"""{d['"']}""", 'dquote') + + self.assertEqual(f'{d["foo"]}', 'bar') + self.assertEqual(f"{d['foo']}", 'bar') + +if __name__ == '__main__': + unittest.main() |