Strict Text Template Parsing (STTP)

• Installation
  • Development
• Quick start
• Motivation
  • Fail fast
• Examples
  • Hello world
  • Hello tables
  • Ping
  • Cisco “show neighbors” example
  • Cisco MPLS forwarding table example
• Templating reference
  • Prefixes
  • Core matches
  • Core function matches
  • Functions
• Matches
  • Making your own match
  • Giving it a type
  • Adding post processing
  • To post process or not to post process
• Function matches
  • Making your own match function
• Regex matches

Demo

The goal of STTP so to make strict parsing easy. Imagine taking some text that you want to parse and simply editing it to mark up where bits change with regular expressions, and specify where lines can be repeated, then use that as a template for parsing to get out the data you want. The parse will succeed if the template matches, and fail if it doesn’t. That’s the core of what STTP does.

Here’s a sample input to make an example out of:

Num   Server               Uptime
1     wibble.domain.com    1d 5h
2     zap.domain.com       100d 1h
3     foobar.domain.com    3d 10h

The following template will parse it:

m> Num   Server               Uptime
m*> {{ int num = integer }}{{ ws }}{{ server = non_ws }}{{ ws }}{{ uptime = string }}

The first m (for match) prefixed line requires STTP to match the given line exactly. The second line’s prefix is the same except there is an asterix. This is regular expression style notation and means “match zero or more times”. The rest of the line is composed of bits inside double curley brackets, and each of those bits amounts to a regular expression, and optionally a variable name which is used to catalogue the matched data. The result of parsing the above text with the above template is this:

[
    {'num': 1, 'server': 'wibble.domain.com', 'uptime': '1d 5h'},
    {'num': 2, 'server': 'zap.domain.com',    'uptime': '100d 1h'},
    {'num': 3, 'server': 'foobar.domain.com', 'uptime': '3d 10h'}
]

The parsing is done simply like this:

parser     = sttp.Parser(template = in_template)
out_struct = parser.parse(in_text)

Here’s a full working example showing the whole thing working:

>>> import sttp
>>>
>>> in_template = '''m> Num   Server               Uptime
... m*> {{ num = integer }}{{ ws }}{{ server = non_ws }}{{ ws }}{{ uptime = string }}
... '''
>>>
>>> in_text = '''Num   Server               Uptime
... 1     wibble.domain.com    1d 5h
... 2     zap.domain.com       100d 1h
... 3     foobar.domain.com    3d 10h
... '''
>>>
>>> parser     = sttp.Parser(template = in_template)
>>> out_struct = parser.parse(in_text)
>>>
>>> assert out_struct == [
...     {'num': 1, 'server': 'wibble.domain.com', 'uptime': '1d 5h'},
...     {'num': 2, 'server': 'zap.domain.com',    'uptime': '100d 1h'},
...     {'num': 3, 'server': 'foobar.domain.com', 'uptime': '3d 10h'}
... ]

Notice that the first column is actually an integer, not a string of digits. This is part of the behaviour of the integer match.