mypy.checkstrformat

module documentation

(source)

Format expression type checker.

This file is conceptually part of ExpressionChecker and TypeChecker. Main functionality is located in StringFormatterChecker.check_str_format_call() for '{}'.format(), and in StringFormatterChecker.check_str_interpolation() for printf-style % interpolation.

Note that although at runtime format strings are parsed using custom parsers, here we use a regexp-based approach. This way we 99% match runtime behaviour while keeping implementation simple.

Class	`ConversionSpecifier`	Undocumented
Class	`StringFormatterChecker`	String interpolation/formatter type checker.
Function	`compile_format_re`	Construct regexp to match format conversion specifiers in % interpolation.
Function	`compile_new_format_re`	Construct regexps to match format conversion specifiers in str.format() calls.
Function	`find_non_escaped_targets`	Return list of raw (un-parsed) format specifiers in format string.
Function	`has_type_component`	Is this a specific instance type, or a union that contains it?
Function	`parse_conversion_specifiers`	Parse c-printf-style format string into list of conversion specifiers.
Function	`parse_format_value`	Parse format string into list of conversion specifiers.
Constant	`DUMMY_FIELD_NAME`	Undocumented
Constant	`FLOAT_TYPES`	Undocumented
Constant	`FORMAT_RE`	Undocumented
Constant	`FORMAT_RE_NEW`	Undocumented
Constant	`FORMAT_RE_NEW_CUSTOM`	Undocumented
Constant	`NUMERIC_TYPES_NEW`	Undocumented
Constant	`NUMERIC_TYPES_OLD`	Undocumented
Constant	`REQUIRE_INT_NEW`	Undocumented
Constant	`REQUIRE_INT_OLD`	Undocumented
Constant	`SUPPORTED_TYPES_NEW`	Undocumented
Variable	`Checkers`	Undocumented
Variable	`FormatStringExpr`	Undocumented
Variable	`MatchMap`	Undocumented

def compile_format_re(): (source)

Construct regexp to match format conversion specifiers in % interpolation.

See https://docs.python.org/3/library/stdtypes.html#printf-style-string-formatting The regexp is intentionally a bit wider to report better errors.

Returns
`Pattern[str]`	Undocumented

def compile_new_format_re(custom_spec): (source)

Construct regexps to match format conversion specifiers in str.format() calls.

See After https://docs.python.org/3/library/string.html#formatspec for specifications. The regexps are intentionally wider, to report better errors, instead of just not matching.

Parameters
custom_spec:`bool`	Undocumented
Returns
`Pattern[str]`	Undocumented

def find_non_escaped_targets(format_value, ctx, msg): (source)

Return list of raw (un-parsed) format specifiers in format string.

Format specifiers don't include enclosing braces. We don't use regexp for this because they don't work well with nested/repeated patterns (both greedy and non-greedy), and these are heavily used internally for representation of f-strings.

Return None in case of an error.

Parameters
format_value:`str`	Undocumented
ctx:`Context`	Undocumented
msg:`MessageBuilder`	Undocumented
Returns
`Optional[List[Tuple[str, int]]]`	Undocumented

def has_type_component(typ, fullname): (source)

Is this a specific instance type, or a union that contains it?

We use this ad-hoc function instead of a proper visitor or subtype check because some str vs bytes errors are strictly speaking not runtime errors, but rather highly counter-intuitive behavior. This is similar to what is used for --strict-equality.

Parameters
typ:`Type`	Undocumented
fullname:`str`	Undocumented
Returns
`bool`	Undocumented

def parse_conversion_specifiers(format_str): (source)

Parse c-printf-style format string into list of conversion specifiers.

Parameters
format_str:`str`	Undocumented
Returns
`List[ConversionSpecifier]`	Undocumented

def parse_format_value(format_value, ctx, msg, nested=False): (source)

Parse format string into list of conversion specifiers.

The specifiers may be nested (two levels maximum), in this case they are ordered as '{0:{1}}, {2:{3}{4}}'. Return None in case of an error.

Parameters
format_value:`str`	Undocumented
ctx:`Context`	Undocumented
msg:`MessageBuilder`	Undocumented
nested:`bool`	Undocumented
Returns
`Optional[List[ConversionSpecifier]]`	Undocumented

DUMMY_FIELD_NAME: str = (source)

Undocumented

Value

'__dummy_name__'

FLOAT_TYPES: set[str] = (source)

Undocumented

Value

set(['e', 'E', 'f', 'F', 'g', 'G'])

FORMAT_RE = (source)

Undocumented

Value

compile_format_re()

FORMAT_RE_NEW = (source)

Undocumented

Value

compile_new_format_re(False)

FORMAT_RE_NEW_CUSTOM = (source)

Undocumented

Value

compile_new_format_re(True)

NUMERIC_TYPES_NEW: set[str] = (source)

Undocumented

Value

set(['b', 'd', 'o', 'e', 'E', 'f', 'F', 'g', 'G', 'n', 'x', 'X', '%'])

NUMERIC_TYPES_OLD: set[str] = (source)

Undocumented

Value

set(['d', 'i', 'o', 'u', 'x', 'X', 'e', 'E', 'f', 'F', 'g', 'G'])

REQUIRE_INT_NEW: set[str] = (source)

Undocumented

Value

set(['b', 'd', 'o', 'x', 'X'])

REQUIRE_INT_OLD: set[str] = (source)

Undocumented

Value

set(['o', 'x', 'X'])

SUPPORTED_TYPES_NEW: set[str] = (source)

Undocumented

Value

set(['b', 'c', 'd', 'e', 'E', 'f', 'F', 'g', 'G', 'n', 'o', 's', 'x', 'X', '%'])

Checkers: _TypeAlias = (source)

Undocumented

FormatStringExpr: _TypeAlias = (source)

Undocumented

MatchMap: _TypeAlias = (source)

Undocumented