headerparser 0.2.0

The Format

RFC 822-style headers are header fields that follow the general format of e-mail headers as specified by RFC 822 and friends: each field is a line of the form “Name: Value”, with long values continued onto multiple lines (“folded”) by indenting the extra lines. A blank line marks the end of the header section and the beginning of the message body.

This basic grammar has been used by numerous textual formats besides e-mail, including but not limited to:

• HTTP request & response headers

• Usenet messages

• most Python packaging metadata files

• Debian packaging control files

• META-INF/MANIFEST.MF files in Java JARs

• a subset of the YAML serialization format

— all of which this package can parse.

Installation

Just use pip (You have pip, right?) to install headerparser and its dependencies:

pip install headerparser

Examples

Define a parser:

>>> import headerparser
>>> parser = headerparser.HeaderParser()
>>> parser.add_field('Name', required=True)
>>> parser.add_field('Type', choices=['example', 'demonstration', 'prototype'], default='example')
>>> parser.add_field('Public', type=headerparser.BOOL, default=False)
>>> parser.add_field('Tag', multiple=True)
>>> parser.add_field('Data')

Parse some headers and inspect the results:

>>> msg = parser.parse_string('''\
... Name: Sample Input
... Public: yes
... tag: doctest, examples,
...   whatever
... TAG: README
...
... Wait, why I am using a body instead of the "Data" field?
... ''')
>>> sorted(msg.keys())
['Name', 'Public', 'Tag', 'Type']
>>> msg['Name']
'Sample Input'
>>> msg['Public']
True
>>> msg['Tag']
['doctest, examples,\n  whatever', 'README']
>>> msg['TYPE']
'example'
>>> msg['Data']
Traceback (most recent call last):
    ...
KeyError: 'data'
>>> msg.body
'Wait, why I am using a body instead of the "Data" field?\n'

Fail to parse headers that don’t meet your requirements:

>>> parser.parse_string('Type: demonstration')
Traceback (most recent call last):
    ...
headerparser.errors.MissingFieldError: Required header field 'Name' is not present
>>> parser.parse_string('Name: Bad type\nType: other')
Traceback (most recent call last):
    ...
headerparser.errors.InvalidChoiceError: 'other' is not a valid choice for 'Type'
>>> parser.parse_string('Name: unknown field\nField: Value')
Traceback (most recent call last):
    ...
headerparser.errors.UnknownFieldError: Unknown header field 'Field'

Allow fields you didn’t even think of:

>>> parser.add_additional()
>>> msg = parser.parse_string('Name: unknown field\nField: Value')
>>> msg['Field']
'Value'

Just split some headers into names & values and worry about validity later:

>>> for field in headerparser.scan_string('''\
... Name: Scanner Sample
... Unknown headers: no problem
... Unparsed-Boolean: yes
... CaSe-SeNsItIvE-rEsUlTs: true
... Whitespace around colons:optional
... Whitespace around colons  :  I already said it's optional.
...   That means you have the _option_ to use as much as you want!
...
... And there's a body, too, I guess.
... '''): print(field)
('Name', 'Scanner Sample')
('Unknown headers', 'no problem')
('Unparsed-Boolean', 'yes')
('CaSe-SeNsItIvE-rEsUlTs', 'true')
('Whitespace around colons', 'optional')
('Whitespace around colons', "I already said it's optional.\n  That means you have the _option_ to use as much as you want!")
(None, "And there's a body, too, I guess.\n")