Parse strings using a specification based on the Python format() syntax.

parse() is the opposite of format()

The module is set up to only export parse() , search() , findall() , and with_pattern() when import \* is used:

>>> from parse import *

From there it’s a simple thing to parse a string:

>>> parse ( "It's {} , I love it!" , "It's spam, I love it!" ) <Result ('spam',) {}> >>> _ [ 0 ] 'spam'

Or to search a string for some pattern:

>>> search ( 'Age: {:d}

' , 'Name: Rufus

Age: 42

Color: red

' ) <Result (42,) {}>

Or find all the occurrences of some pattern in a string:

>>> '' . join ( r [ 0 ] for r in findall ( "> {} <" , "<p>the <b>bold</b> text</p>" )) 'the bold text'

If you’re going to use the same pattern to match lots of strings you can compile it once:

>>> from parse import compile >>> p = compile ( "It's {} , I love it!" ) >>> print ( p ) <Parser "It's {}, I love it!"> >>> p . parse ( "It's spam, I love it!" ) <Result ('spam',) {}>

(“compile” is not exported for import * usage as it would override the built-in compile() function)

The default behaviour is to match strings case insensitively. You may match with case by specifying case_sensitive=True :

>>> parse ( 'SPAM' , 'spam' , case_sensitive = True ) is None True

Format Syntax A basic version of the Format String Syntax is supported with anonymous (fixed-position), named and formatted fields: {[field name]:[format spec]} Field names must be a valid Python identifiers, including dotted names; element indexes imply dictionaries (see below for example). Numbered fields are also not supported: the result of parsing will include the parsed fields in the order they are parsed. The conversion of fields to types other than strings is done based on the type in the format specification, which mirrors the format() behaviour. There are no “!” field conversions like format() has. Some simple parse() format string examples: >>> parse ( "Bring me a {} " , "Bring me a shrubbery" ) <Result ('shrubbery',) {}> >>> r = parse ( "The {} who say {} " , "The knights who say Ni!" ) >>> print ( r ) <Result ('knights', 'Ni!') {}> >>> print ( r . fixed ) ('knights', 'Ni!') >>> r = parse ( "Bring out the holy {item} " , "Bring out the holy hand grenade" ) >>> print ( r ) <Result () {'item': 'hand grenade'}> >>> print ( r . named ) {'item': 'hand grenade'} >>> print ( r [ 'item' ]) hand grenade >>> 'item' in r True Note that in only works if you have named fields. Dotted names and indexes are possible though the application must make additional sense of the result: >>> r = parse ( "Mmm, {food.type} , I love it!" , "Mmm, spam, I love it!" ) >>> print ( r ) <Result () {'food.type': 'spam'}> >>> print ( r . named ) {'food.type': 'spam'} >>> print ( r [ 'food.type' ]) spam >>> r = parse ( "My quest is {quest[name]} " , "My quest is to seek the holy grail!" ) >>> print ( r ) <Result () {'quest': {'name': 'to seek the holy grail!'}}> >>> print ( r [ 'quest' ]) {'name': 'to seek the holy grail!'} >>> print ( r [ 'quest' ][ 'name' ]) to seek the holy grail! If the text you’re matching has braces in it you can match those by including a double-brace {{ or }} in your format string, just like format() does.

Format Specification Most often a straight format-less {} will suffice where a more complex format specification might have been used. Most of format() ’s Format Specification Mini-Language is supported: [[fill]align][0][width][.precision][type] The differences between parse() and format() are: The align operators will cause spaces (or specified fill character) to be stripped from the parsed value. The width is not enforced; it just indicates there may be whitespace or “0”s to strip.

Numeric parsing will automatically handle a “0b”, “0o” or “0x” prefix. That is, the “#” format character is handled automatically by d, b, o and x formats. For “d” any will be accepted, but for the others the correct prefix must be present if at all.

Numeric sign is handled automatically.

The thousands separator is handled automatically if the “n” type is used.

The types supported are a slightly different mix to the format() types. Some format() types come directly over: “d”, “n”, “%”, “f”, “e”, “b”, “o” and “x”. In addition some regular expression character group types “D”, “w”, “W”, “s” and “S” are also available.

The “e” and “g” types are case-insensitive so there is not need for the “E” or “G” types. The “e” type handles Fortran formatted numbers (no leading 0 before the decimal point). Type Characters Matched Output l Letters (ASCII) str w Letters, numbers and underscore str W Not letters, numbers and underscore str s Whitespace str S Non-whitespace str d Digits (effectively integer numbers) int D Non-digit str n Numbers with thousands separators (, or .) int % Percentage (converted to value/100.0) float f Fixed-point numbers float F Decimal numbers Decimal e Floating-point numbers with exponent e.g. 1.1e-10, NAN (all case insensitive) float g General number format (either d, f or e) float b Binary numbers int o Octal numbers int x Hexadecimal numbers (lower and upper case) int ti ISO 8601 format date/time e.g. 1972-01-20T10:21:36Z (“T” and “Z” optional) datetime te RFC2822 e-mail format date/time e.g. Mon, 20 Jan 1972 10:21:36 +1000 datetime tg Global (day/month) format date/time e.g. 20/1/1972 10:21:36 AM +1:00 datetime ta US (month/day) format date/time e.g. 1/20/1972 10:21:36 PM +10:30 datetime tc ctime() format date/time e.g. Sun Sep 16 01:03:52 1973 datetime th HTTP log format date/time e.g. 21/Nov/2011:00:07:11 +0000 datetime ts Linux system log format date/time e.g. Nov 9 03:37:44 datetime tt Time e.g. 10:21:36 PM -5:30 time Some examples of typed parsing with None returned if the typing does not match: >>> parse ( 'Our {:d} {:w} are...' , 'Our 3 weapons are...' ) <Result (3, 'weapons') {}> >>> parse ( 'Our {:d} {:w} are...' , 'Our three weapons are...' ) >>> parse ( 'Meet at {:tg}' , 'Meet at 1/2/2011 11:00 PM' ) <Result (datetime.datetime(2011, 2, 1, 23, 0),) {}> And messing about with alignment: >>> parse ( 'with {:>} herring' , 'with a herring' ) <Result ('a',) {}> >>> parse ( 'spam {:^} spam' , 'spam lovely spam' ) <Result ('lovely',) {}> Note that the “center” alignment does not test to make sure the value is centered - it just strips leading and trailing whitespace. Width and precision may be used to restrict the size of matched text from the input. Width specifies a minimum size and precision specifies a maximum. For example: >>> parse ( ' {:.2}{:.2} ' , 'look' ) # specifying precision <Result ('lo', 'ok') {}> >>> parse ( ' {:4}{:4} ' , 'look at that' ) # specifying width <Result ('look', 'at that') {}> >>> parse ( ' {:4}{:.4} ' , 'look at that' ) # specifying both <Result ('look at ', 'that') {}> >>> parse ( ' {:2d}{:2d} ' , '0440' ) # parsing two contiguous numbers <Result (4, 40) {}> Some notes for the date and time types: the presence of the time part is optional (including ISO 8601, starting at the “T”). A full datetime object will always be returned; the time will be set to 00:00:00. You may also specify a time without seconds.

when a seconds amount is present in the input fractions will be parsed to give microseconds.

except in ISO 8601 the day and month digits may be 0-padded.

the date separator for the tg and ta formats may be “-” or “/”.

named months (abbreviations or full names) may be used in the ta and tg formats in place of numeric months.

as per RFC 2822 the e-mail format may omit the day (and comma), and the seconds but nothing else.

hours greater than 12 will be happily accepted.

the AM/PM are optional, and if PM is found then 12 hours will be added to the datetime object’s hours amount - even if the hour is greater than 12 (for consistency.)

in ISO 8601 the “Z” (UTC) timezone part may be a numeric offset

timezones are specified as “+HH:MM” or “-HH:MM”. The hour may be one or two digits (0-padded is OK.) Also, the “:” is optional.

the timezone is optional in all except the e-mail format (it defaults to UTC.)

named timezones are not handled yet. Note: attempting to match too many datetime fields in a single parse() will currently result in a resource allocation issue. A TooManyFields exception will be raised in this instance. The current limit is about 15. It is hoped that this limit will be removed one day.

Result and Match Objects The result of a parse() and search() operation is either None (no match), a Result instance or a Match instance if evaluate_result is False. The Result instance has three attributes: fixed A tuple of the fixed-position, anonymous fields extracted from the input. named A dictionary of the named fields extracted from the input. spans A dictionary mapping the names and fixed position indices matched to a 2-tuple slice range of where the match occurred in the input. The span does not include any stripped padding (alignment or width). The Match instance has one method: evaluate_result() Generates and returns a Result instance for this Match object.

Custom Type Conversions If you wish to have matched fields automatically converted to your own type you may pass in a dictionary of type conversion information to parse() and compile() . The converter will be passed the field string matched. Whatever it returns will be substituted in the Result instance for that field. Your custom type conversions may override the builtin types if you supply one with the same identifier: >>> def shouty ( string ): ... return string . upper () ... >>> parse ( '{:shouty} world' , 'hello world' , dict ( shouty = shouty )) <Result ('HELLO',) {}> If the type converter has the optional pattern attribute, it is used as regular expression for better pattern matching (instead of the default one): >>> def parse_number ( text ): ... return int ( text ) >>> parse_number . pattern = r '\d+' >>> parse ( 'Answer: {number:Number}' , 'Answer: 42' , dict ( Number = parse_number )) <Result () {'number': 42}> >>> _ = parse ( 'Answer: {:Number}' , 'Answer: Alice' , dict ( Number = parse_number )) >>> assert _ is None , "MISMATCH" You can also use the with_pattern(pattern) decorator to add this information to a type converter function: >>> from parse import with_pattern >>> @with_pattern ( r '\d+' ) ... def parse_number ( text ): ... return int ( text ) >>> parse ( 'Answer: {number:Number}' , 'Answer: 42' , dict ( Number = parse_number )) <Result () {'number': 42}> A more complete example of a custom type might be: >>> yesno_mapping = { ... "yes" : True , "no" : False , ... "on" : True , "off" : False , ... "true" : True , "false" : False , ... } >>> @with_pattern ( r "|" . join ( yesno_mapping )) ... def parse_yesno ( text ): ... return yesno_mapping [ text . lower ()] If the type converter pattern uses regex-grouping (with parenthesis), you should indicate this by using the optional regex_group_count parameter in the with_pattern() decorator: >>> @with_pattern ( r '((\d+))' , regex_group_count = 2 ) ... def parse_number2 ( text ): ... return int ( text ) >>> parse ( 'Answer: {:Number2} {:Number2}' , 'Answer: 42 43' , dict ( Number2 = parse_number2 )) <Result (42, 43) {}> Otherwise, this may cause parsing problems with unnamed/fixed parameters.