cpython/Lib/test/test_fstring.py at b4fb7ef321e1db9bafb7ec4bc442b5fb6aa3071f · shihai1991/cpython

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# -*- coding: utf-8 -*-

# There are tests here with unicode string literals and

# identifiers. There's a code in ast.c that was added because of a

# failure with a non-ascii-only expression. So, I have tests for

# that. There are workarounds that would let me run tests for that

# code without unicode identifiers and strings, but just using them

# directly seems like the easiest and therefore safest thing to do.

# Unicode identifiers in tests is allowed by PEP 3131.

import ast

import os

import types

import decimal

import unittest

from test.support.os_helper import temp_cwd

from test.support.script_helper import assert_python_failure

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_ast_line_numbers(self):

expr = """

a = 10

f'{a * x()}'"""

t = ast.parse(expr)

self.assertEqual(type(t), ast.Module)

self.assertEqual(len(t.body), 2)

# check `a = 10`

self.assertEqual(type(t.body[0]), ast.Assign)

self.assertEqual(t.body[0].lineno, 2)

# check `f'...'`

self.assertEqual(type(t.body[1]), ast.Expr)

self.assertEqual(type(t.body[1].value), ast.JoinedStr)

self.assertEqual(len(t.body[1].value.values), 1)

self.assertEqual(type(t.body[1].value.values[0]), ast.FormattedValue)

self.assertEqual(t.body[1].lineno, 3)

self.assertEqual(t.body[1].value.lineno, 3)

self.assertEqual(t.body[1].value.values[0].lineno, 3)

# check the binop location

binop = t.body[1].value.values[0].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.Call)

self.assertEqual(binop.lineno, 3)

self.assertEqual(binop.left.lineno, 3)

self.assertEqual(binop.right.lineno, 3)

self.assertEqual(binop.col_offset, 3)

self.assertEqual(binop.left.col_offset, 3)

self.assertEqual(binop.right.col_offset, 7)

def test_ast_line_numbers_multiple_formattedvalues(self):

expr = """

f'no formatted values'

f'eggs {a * x()} spam {b + y()}'"""

t = ast.parse(expr)

self.assertEqual(type(t), ast.Module)

self.assertEqual(len(t.body), 2)

# check `f'no formatted value'`

self.assertEqual(type(t.body[0]), ast.Expr)

self.assertEqual(type(t.body[0].value), ast.JoinedStr)

self.assertEqual(t.body[0].lineno, 2)

# check `f'...'`

self.assertEqual(type(t.body[1]), ast.Expr)

self.assertEqual(type(t.body[1].value), ast.JoinedStr)

self.assertEqual(len(t.body[1].value.values), 4)

self.assertEqual(type(t.body[1].value.values[0]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[0].value), str)

self.assertEqual(type(t.body[1].value.values[1]), ast.FormattedValue)

self.assertEqual(type(t.body[1].value.values[2]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[2].value), str)

self.assertEqual(type(t.body[1].value.values[3]), ast.FormattedValue)

self.assertEqual(t.body[1].lineno, 3)

self.assertEqual(t.body[1].value.lineno, 3)

self.assertEqual(t.body[1].value.values[0].lineno, 3)

self.assertEqual(t.body[1].value.values[1].lineno, 3)

self.assertEqual(t.body[1].value.values[2].lineno, 3)

self.assertEqual(t.body[1].value.values[3].lineno, 3)

# check the first binop location

binop1 = t.body[1].value.values[1].value

self.assertEqual(type(binop1), ast.BinOp)

self.assertEqual(type(binop1.left), ast.Name)

self.assertEqual(type(binop1.op), ast.Mult)

self.assertEqual(type(binop1.right), ast.Call)

self.assertEqual(binop1.lineno, 3)

self.assertEqual(binop1.left.lineno, 3)

self.assertEqual(binop1.right.lineno, 3)

self.assertEqual(binop1.col_offset, 8)

self.assertEqual(binop1.left.col_offset, 8)

self.assertEqual(binop1.right.col_offset, 12)

# check the second binop location

binop2 = t.body[1].value.values[3].value

self.assertEqual(type(binop2), ast.BinOp)

self.assertEqual(type(binop2.left), ast.Name)

self.assertEqual(type(binop2.op), ast.Add)

self.assertEqual(type(binop2.right), ast.Call)

self.assertEqual(binop2.lineno, 3)

self.assertEqual(binop2.left.lineno, 3)

self.assertEqual(binop2.right.lineno, 3)

self.assertEqual(binop2.col_offset, 23)

self.assertEqual(binop2.left.col_offset, 23)

self.assertEqual(binop2.right.col_offset, 27)

def test_ast_line_numbers_nested(self):

expr = """

a = 10

f'{a * f"-{x()}-"}'"""

t = ast.parse(expr)

self.assertEqual(type(t), ast.Module)

self.assertEqual(len(t.body), 2)

# check `a = 10`

self.assertEqual(type(t.body[0]), ast.Assign)

self.assertEqual(t.body[0].lineno, 2)

# check `f'...'`

self.assertEqual(type(t.body[1]), ast.Expr)

self.assertEqual(type(t.body[1].value), ast.JoinedStr)

self.assertEqual(len(t.body[1].value.values), 1)

self.assertEqual(type(t.body[1].value.values[0]), ast.FormattedValue)

self.assertEqual(t.body[1].lineno, 3)

self.assertEqual(t.body[1].value.lineno, 3)

self.assertEqual(t.body[1].value.values[0].lineno, 3)

# check the binop location

binop = t.body[1].value.values[0].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.JoinedStr)

self.assertEqual(binop.lineno, 3)

self.assertEqual(binop.left.lineno, 3)

self.assertEqual(binop.right.lineno, 3)

self.assertEqual(binop.col_offset, 3)

self.assertEqual(binop.left.col_offset, 3)

self.assertEqual(binop.right.col_offset, 7)

# check the nested call location

self.assertEqual(len(binop.right.values), 3)

self.assertEqual(type(binop.right.values[0]), ast.Constant)

self.assertEqual(type(binop.right.values[0].value), str)

self.assertEqual(type(binop.right.values[1]), ast.FormattedValue)

self.assertEqual(type(binop.right.values[2]), ast.Constant)

self.assertEqual(type(binop.right.values[2].value), str)

self.assertEqual(binop.right.values[0].lineno, 3)

self.assertEqual(binop.right.values[1].lineno, 3)

self.assertEqual(binop.right.values[2].lineno, 3)

call = binop.right.values[1].value

self.assertEqual(type(call), ast.Call)

self.assertEqual(call.lineno, 3)

self.assertEqual(call.col_offset, 11)

def test_ast_line_numbers_duplicate_expression(self):

"""Duplicate expression

NOTE: this is currently broken, always sets location of the first

expression.

"""

expr = """

a = 10

f'{a * x()} {a * x()} {a * x()}'

"""

t = ast.parse(expr)

self.assertEqual(type(t), ast.Module)

self.assertEqual(len(t.body), 2)

# check `a = 10`

self.assertEqual(type(t.body[0]), ast.Assign)

self.assertEqual(t.body[0].lineno, 2)

# check `f'...'`

self.assertEqual(type(t.body[1]), ast.Expr)

self.assertEqual(type(t.body[1].value), ast.JoinedStr)

self.assertEqual(len(t.body[1].value.values), 5)

self.assertEqual(type(t.body[1].value.values[0]), ast.FormattedValue)

self.assertEqual(type(t.body[1].value.values[1]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[1].value), str)

self.assertEqual(type(t.body[1].value.values[2]), ast.FormattedValue)

self.assertEqual(type(t.body[1].value.values[3]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[3].value), str)

self.assertEqual(type(t.body[1].value.values[4]), ast.FormattedValue)

self.assertEqual(t.body[1].lineno, 3)

self.assertEqual(t.body[1].value.lineno, 3)

self.assertEqual(t.body[1].value.values[0].lineno, 3)

self.assertEqual(t.body[1].value.values[1].lineno, 3)

self.assertEqual(t.body[1].value.values[2].lineno, 3)

self.assertEqual(t.body[1].value.values[3].lineno, 3)

self.assertEqual(t.body[1].value.values[4].lineno, 3)

# check the first binop location

binop = t.body[1].value.values[0].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.Call)

self.assertEqual(binop.lineno, 3)

self.assertEqual(binop.left.lineno, 3)

self.assertEqual(binop.right.lineno, 3)

self.assertEqual(binop.col_offset, 3)

self.assertEqual(binop.left.col_offset, 3)

self.assertEqual(binop.right.col_offset, 7)

# check the second binop location

binop = t.body[1].value.values[2].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.Call)

self.assertEqual(binop.lineno, 3)

self.assertEqual(binop.left.lineno, 3)

self.assertEqual(binop.right.lineno, 3)

self.assertEqual(binop.col_offset, 3) # FIXME: this is wrong

self.assertEqual(binop.left.col_offset, 3) # FIXME: this is wrong

self.assertEqual(binop.right.col_offset, 7) # FIXME: this is wrong

# check the third binop location

binop = t.body[1].value.values[4].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.Call)

self.assertEqual(binop.lineno, 3)

self.assertEqual(binop.left.lineno, 3)

self.assertEqual(binop.right.lineno, 3)

self.assertEqual(binop.col_offset, 3) # FIXME: this is wrong

self.assertEqual(binop.left.col_offset, 3) # FIXME: this is wrong

self.assertEqual(binop.right.col_offset, 7) # FIXME: this is wrong

def test_ast_line_numbers_multiline_fstring(self):

# See bpo-30465 for details.

expr = """

a = 10

f'''

x()}

non-important content

'''

"""

t = ast.parse(expr)

self.assertEqual(type(t), ast.Module)

self.assertEqual(len(t.body), 2)

# check `a = 10`

self.assertEqual(type(t.body[0]), ast.Assign)

self.assertEqual(t.body[0].lineno, 2)

# check `f'...'`

self.assertEqual(type(t.body[1]), ast.Expr)

self.assertEqual(type(t.body[1].value), ast.JoinedStr)

self.assertEqual(len(t.body[1].value.values), 3)

self.assertEqual(type(t.body[1].value.values[0]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[0].value), str)

self.assertEqual(type(t.body[1].value.values[1]), ast.FormattedValue)

self.assertEqual(type(t.body[1].value.values[2]), ast.Constant)

self.assertEqual(type(t.body[1].value.values[2].value), str)

self.assertEqual(t.body[1].lineno, 3)

self.assertEqual(t.body[1].value.lineno, 3)

self.assertEqual(t.body[1].value.values[0].lineno, 3)

self.assertEqual(t.body[1].value.values[1].lineno, 3)

self.assertEqual(t.body[1].value.values[2].lineno, 3)

self.assertEqual(t.body[1].col_offset, 0)

self.assertEqual(t.body[1].value.col_offset, 0)

self.assertEqual(t.body[1].value.values[0].col_offset, 0)

self.assertEqual(t.body[1].value.values[1].col_offset, 0)

self.assertEqual(t.body[1].value.values[2].col_offset, 0)

# NOTE: the following lineno information and col_offset is correct for

# expressions within FormattedValues.

binop = t.body[1].value.values[1].value

self.assertEqual(type(binop), ast.BinOp)

self.assertEqual(type(binop.left), ast.Name)

self.assertEqual(type(binop.op), ast.Mult)

self.assertEqual(type(binop.right), ast.Call)

self.assertEqual(binop.lineno, 4)

self.assertEqual(binop.left.lineno, 4)

self.assertEqual(binop.right.lineno, 6)

self.assertEqual(binop.col_offset, 4)

self.assertEqual(binop.left.col_offset, 4)

self.assertEqual(binop.right.col_offset, 7)

def test_docstring(self):

def f():

f'''Not a docstring'''

self.assertIsNone(f.__doc__)

def g():

'''Not a docstring''' \

f''

self.assertIsNone(g.__doc__)

def test_literal_eval(self):

with self.assertRaisesRegex(ValueError, 'malformed node or string'):

ast.literal_eval("f'x'")

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_compile_time_concat_errors(self):

self.assertAllRaise(SyntaxError,

'cannot mix bytes and nonbytes literals',

[r"""f'' b''""",

r"""b'' f''""",

])

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, r"f-string: closing parenthesis '\}' "

r"does not match opening parenthesis '\('",

["f'{((}'",

])

self.assertAllRaise(SyntaxError, r"f-string: closing parenthesis '\)' "

r"does not match opening parenthesis '\['",

["f'{a[4)}'",

])

self.assertAllRaise(SyntaxError, r"f-string: closing parenthesis '\]' "

r"does not match opening parenthesis '\('",

["f'{a(4]}'",

])

self.assertAllRaise(SyntaxError, r"f-string: closing parenthesis '\}' "

r"does not match opening parenthesis '\['",

["f'{a[4}'",

])

self.assertAllRaise(SyntaxError, r"f-string: closing parenthesis '\}' "

r"does not match opening parenthesis '\('",

["f'{a(4}'",

])

self.assertRaises(SyntaxError, eval, "f'{" + "("*500 + "}'")

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'{{}}', '{}')

self.assertEqual(f'a{{}}', 'a{}')

self.assertEqual(f'{{b}}', '{b}')

self.assertEqual(f'{{}}c', '{}c')

self.assertEqual(f'a{{b}}', 'a{b}')

self.assertEqual(f'a{{}}c', 'a{}c')

self.assertEqual(f'{{b}}c', '{b}c')

self.assertEqual(f'a{{b}}c', 'a{b}c')

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 expression part cannot include '#'",

["f'{1#}'", # error because the expression becomes "(1#)"

"f'{3(#)}'",

"f'{#}'",

])

self.assertAllRaise(SyntaxError, r"f-string: unmatched '\)'",

["f'{)#}'", # When wrapped in parens, this becomes

# '()#)'. Make sure that doesn't compile.

])

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, "f-string: 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' { } '",

# The Python parser ignores also the following

# whitespace characters in additional to a space.

"f'''{\t\f\r\n}'''",

# 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'",

])

# Different error message is raised for other whitespace characters.

self.assertAllRaise(SyntaxError, r"invalid non-printable character U\+00A0",

["f'''{\xa0}'''",

"\xa0",

])

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, 'f-string: invalid syntax',

["f'{,}'",

"f'{,}'", # this is (,), which is an error

])

self.assertAllRaise(SyntaxError, r"f-string: unmatched '\)'",

["f'{3)+(4}'",

])

self.assertAllRaise(SyntaxError, 'EOL while scanning string literal',

["f'{\n}'",

])

def test_backslashes_in_string_part(self):

self.assertEqual(f'\t', '\t')

self.assertEqual(r'\t', '\\t')

self.assertEqual(rf'\t', '\\t')

self.assertEqual(f'{2}\t', '2\t')

self.assertEqual(f'{2}\t{3}', '2\t3')

self.assertEqual(f'\t{3}', '\t3')

self.assertEqual(f'\u0394', '\u0394')

self.assertEqual(r'\u0394', '\\u0394')

self.assertEqual(rf'\u0394', '\\u0394')

self.assertEqual(f'{2}\u0394', '2\u0394')

self.assertEqual(f'{2}\u0394{3}', '2\u03943')

self.assertEqual(f'\u0394{3}', '\u03943')

self.assertEqual(f'\U00000394', '\u0394')

self.assertEqual(r'\U00000394', '\\U00000394')

self.assertEqual(rf'\U00000394', '\\U00000394')

self.assertEqual(f'{2}\U00000394', '2\u0394')

self.assertEqual(f'{2}\U00000394{3}', '2\u03943')

self.assertEqual(f'\U00000394{3}', '\u03943')

self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}', '\u0394')

self.assertEqual(f'{2}\N{GREEK CAPITAL LETTER DELTA}', '2\u0394')

self.assertEqual(f'{2}\N{GREEK CAPITAL LETTER DELTA}{3}', '2\u03943')

self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}{3}', '\u03943')

self.assertEqual(f'2\N{GREEK CAPITAL LETTER DELTA}', '2\u0394')

self.assertEqual(f'2\N{GREEK CAPITAL LETTER DELTA}3', '2\u03943')

self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}3', '\u03943')

self.assertEqual(f'\x20', ' ')

self.assertEqual(r'\x20', '\\x20')

self.assertEqual(rf'\x20', '\\x20')

self.assertEqual(f'{2}\x20', '2 ')

self.assertEqual(f'{2}\x20{3}', '2 3')

self.assertEqual(f'\x20{3}', ' 3')

self.assertEqual(f'2\x20', '2 ')

self.assertEqual(f'2\x203', '2 3')

self.assertEqual(f'\x203', ' 3')

with self.assertWarns(DeprecationWarning): # invalid escape sequence

value = eval(r"f'\{6*7}'")

self.assertEqual(value, '\\42')

self.assertEqual(f'\\{6*7}', '\\42')

self.assertEqual(fr'\{6*7}', '\\42')

AMPERSAND = 'spam'

# Get the right unicode character (&), or pick up local variable

# depending on the number of backslashes.

self.assertEqual(f'\N{AMPERSAND}', '&')

self.assertEqual(f'\\N{AMPERSAND}', '\\Nspam')

self.assertEqual(fr'\N{AMPERSAND}', '\\Nspam')

self.assertEqual(f'\\\N{AMPERSAND}', '\\&')

def test_misformed_unicode_character_name(self):

# These test are needed because unicode names are parsed

# differently inside f-strings.

self.assertAllRaise(SyntaxError, r"\(unicode error\) 'unicodeescape' codec can't decode bytes in position .*: malformed \\N character escape",

[r"f'\N'",

r"f'\N{'",

r"f'\N{GREEK CAPITAL LETTER DELTA'",

# Here are the non-f-string versions,

# which should give the same errors.

r"'\N'",

r"'\N{'",

r"'\N{GREEK CAPITAL LETTER DELTA'",

])

def test_no_backslashes_in_expression_part(self):

self.assertAllRaise(SyntaxError, 'f-string expression part cannot include a backslash',

[r"f'{\'a\'}'",

r"f'{\t3}'",

r"f'{\}'",

r"rf'{\'a\'}'",

r"rf'{\t3}'",

r"rf'{\}'",

r"""rf'{"\N{LEFT CURLY BRACKET}"}'""",

r"f'{\n}'",

])

def test_no_escapes_for_braces(self):

"""

Only literal curly braces begin an expression.

"""

# \x7b is '{'.

self.assertEqual(f'\x7b1+1}}', '{1+1}')

self.assertEqual(f'\x7b1+1', '{1+1')

self.assertEqual(f'\u007b1+1', '{1+1')

self.assertEqual(f'\N{LEFT CURLY BRACKET}1+1\N{RIGHT CURLY BRACKET}', '{1+1}')

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, 'f-string: invalid syntax',

["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}'

f'{yield}'

g = fn(4)

self.assertEqual(next(g), 8)

self.assertEqual(next(g), None)

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):

single_quote_cases = ["fu''",

"uf''",

"Fu''",

"fU''",

"Uf''",

"uF''",

"ufr''",

"urf''",

"fur''",

"fru''",

"rfu''",

"ruf''",

"FUR''",

"Fur''",

"fb''",

"fB''",

"Fb''",

"FB''",

"bf''",

"bF''",

"Bf''",

"BF''",]

double_quote_cases = [case.replace("'", '"') for case in single_quote_cases]

self.assertAllRaise(SyntaxError, 'unexpected EOF while parsing',

single_quote_cases + double_quote_cases)

def test_leading_trailing_spaces(self):

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_equal_equal(self):

# Because an expression ending in = has special meaning,

# there's a special test for ==. Make sure it works.

self.assertEqual(f'{0==1}', 'False')

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!3}'",

"f'{3!G}'",

"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'",

r"f'\u007b}'",

# 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'{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}':

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