Python Pyparsing Located vs locatedExpr

Question

I am changing a few pyparsing patterns from pyparsing version 2 to pyparsing version 3.

The contents of the sample file I use for parsing

this is a sample page to test parsing
line 0001 line 1
line 0002 line 2

the pattern used to create parser

p.Literal('line ') + p.Regex(r'(?P<abc>\d+)') + p.SkipTo(p.LineEnd().suppress())

When I using the locatedExpr from version2 I get the following output

{'locn_start': 55, 'abc': '0002', 'value': ['line ', '0002', ' line 2'], 'locn_end': 71}

when I use Located from version 3 I get the following output for the same pattern

{'locn_start': 55, 'value': {'abc': '0002'}, 'locn_end': 71}

However if I remove the named capturing group from the pattern like below example

[p.Literal('line ') + p.Regex(r'\d+')] + p.SkipTo(p.LineEnd().suppress())

I get the same output as locatedExpr

{'locn_start': 55, 'value': ['line ', '0002', ' line 2'], 'locn_end': 71}

However I like to group the information in my parsing and I was wondering if anybody know the difference between Located and locatedExpr

In all the above cases I am using parse_with_tabs

What is the purpose of the []'s in [p.Literal('line ') + p.Regex(r'\d+')] + p.SkipTo(p.LineEnd().suppress())? — PaulMcG
– PaulMcG, Commented Apr 16, 2023 at 23:26
locatedExpr is deprecated in favor of Located, introduced in 3.0.0. — PaulMcG
– PaulMcG, Commented Apr 16, 2023 at 23:41
Why did you edit the question so severely? Don't make it non understandable. — mozway
– mozway, Commented Apr 19, 2023 at 20:58

PaulMcG · Accepted Answer · 2023-04-16 23:40:35Z

I think you may be using as_dict() to view the contents of the parsed results. as_dict() does not display unnamed elements in the results. Please use the dump() method instead. Pyparsing's run_tests method uses dump() to display the parsed results:

import pyparsing as p

tests = """
    line 0002 line 2
"""

parser = p.Literal('line ') + p.Regex(r'(?P<abc>\d+)') + p.SkipTo(p.LineEnd().suppress())
p.Located(parser).run_tests(tests)
p.locatedExpr(parser).run_tests(tests)

parser = p.Literal('line ') + p.Regex(r'\d+') + p.SkipTo(p.LineEnd().suppress())
p.Located(parser).run_tests(tests)
p.locatedExpr(parser).run_tests(tests)

prints

line 0002 line 2
[0, ['line ', '0002', 'line 2'], 16]
- locn_end: 16
- locn_start: 0
- value: ['line ', '0002', 'line 2']
  - abc: '0002'
[0]:
  0
[1]:
  ['line ', '0002', 'line 2']
  - abc: '0002'
[2]:
  16

line 0002 line 2
[[0, 'line ', '0002', 'line 2', 16]]
[0]:
  [0, 'line ', '0002', 'line 2', 16]
  - abc: '0002'
  - locn_end: 16
  - locn_start: 0
  - value: ['line ', '0002', 'line 2']

line 0002 line 2
[0, ['line ', '0002', 'line 2'], 16]
- locn_end: 16
- locn_start: 0
- value: ['line ', '0002', 'line 2']
[0]:
  0
[1]:
  ['line ', '0002', 'line 2']
[2]:
  16

line 0002 line 2
[[0, 'line ', '0002', 'line 2', 16]]
[0]:
  [0, 'line ', '0002', 'line 2', 16]
  - locn_end: 16
  - locn_start: 0
  - value: ['line ', '0002', 'line 2']

The new Located class is more consistent in how it reports the parsed value, whether it does or does not contain any named items or regex groups.

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