parse
parse() is the opposite of format()
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Description
Installation
------------
.. code-block:: pycon
pip install parse
Usage
-----
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:
.. code-block:: pycon
>>> parse("It's {}, I love it!", "It's spam, I love it!")
<Result ('spam',) {}>
>>> _[0]
'spam'
Or to search a string for some pattern:
.. code-block:: pycon
>>> search('Age: {:d}\n', 'Name: Rufus\nAge: 42\nColor: red\n')
<Result (42,) {}>
Or find all the occurrences of some pattern in a string:
.. code-block:: pycon
>>> ''.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:
.. code-block:: pycon
>>> 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`:
.. code-block:: pycon
>>> parse('SPAM', 'spam', case_sensitive=True) is None
True
.. _format():
https://docs.python.org/3/library/stdtypes.html#str.format
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:
.. code-block:: pycon
>>> parse("Bring me a {}", "Bring me a shrubbery")
<Result ('shrubbery',) {}>
>>> r = parse("The {} who {} {}", "The knights who say Ni!")
>>> print(r)
<Result ('knights', 'say', 'Ni!') {}>
>>> print(r.fixed)
('knights', 'say', 'Ni!')
>>> print(r[0])
knights
>>> print(r[1:])
('say', '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 with some limits. Only word identifiers
are supported (ie. no numeric indexes) and the application must make additional
sense of the result:
.. code-block:: pycon
>>> 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, the same escaping method
used in the ``format()`` syntax.
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][sign][0][width][grouping][.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. A sign specifier can be given, but
has no effect.
- 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 Integer numbers (optional sign, digits) 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 float
e.g. 1.1e-10, NAN (all case insensitive)
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 datetime
e.g. 1972-01-20T10:21:36Z ("T" and "Z"
optional)
te RFC2822 e-mail format date/time datetime
e.g. Mon, 20 Jan 1972 10:21:36 +1000
tg Global (day/month) format date/time datetime
e.g. 20/1/1972 10:21:36 AM +1:00
ta US (month/day) format date/time datetime
e.g. 1/20/1972 10:21:36 PM +10:30
tc ctime() format date/time datetime
e.g. Sun Sep 16 01:03:52 1973
th HTTP log format date/time datetime
e.g. 21/Nov/2011:00:07:11 +0000
ts Linux system log format date/time datetime
e.g. Nov 9 03:37:44
tt Time time
e.g. 10:21:36 PM -5:30
===== =========================================== ========
The type can also be a datetime format string, following the
`1989 C standard format codes`_, e.g. ``%Y-%m-%d``. Depending on the
directives contained in the format string, parsed output may be an instance
of ``datetime.datetime``, ``datetime.time``, or ``datetime.date``.
.. code-block:: pycon
>>> parse("{:%Y-%m-%d %H:%M:%S}", "2023-11-23 12:56:47")
<Result (datetime.datetime(2023, 11, 23, 12, 56, 47),) {}>
>>> parse("{:%H:%M}", "10:26")
<Result (datetime.time(10, 26),) {}>
>>> parse("{:%Y/%m/%d}", "2023/11/25")
<Result (datetime.date(2023, 11, 25),) {}>
Some examples of typed parsing with ``None`` returned if the typing
does not match:
.. code-block:: pycon
>>> 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:
.. code-block:: pycon
>>> 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:
.. code-block:: pycon
>>> 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 special 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 b