python - How to a match any sequence of text until "#{" in pyparsing - Stack Overflow

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I want to do string templating with py parsing. I have failed multiple times to define a grammar that can parse a string with inserted text inbetween "#{" and "}" (seems pretty basic) :

Example of grammar which doesn't work :

from pyparsing import CharsNotIn, FollowedBy, Group, Literal, OneOrMore, Suppress
# Define the unwanted sequence
hash_tag = Suppress(Literal('#{')) + CharsNotIn('}') + Suppress(Literal('}'))
text_part = CharsNotIn('#{')
# Combine the parts to match the entire string
parser = OneOrMore(Group(hash_tag) | text_part)
test_string = "Some text \n with a stranded # and a stranded { then a correct #{ insertion of \n some # other text } and then some text"

result = parser.searchString(test_string)
expected_result = ["Some text \n with a stranded # and a stranded { then a correct ",[" insertion of \n some # other text "]," and then some text"]
print(result)

The result is not the expected result (I get ["Some text \n with a stranded "])

I want to do string templating with py parsing. I have failed multiple times to define a grammar that can parse a string with inserted text inbetween "#{" and "}" (seems pretty basic) :

Example of grammar which doesn't work :

from pyparsing import CharsNotIn, FollowedBy, Group, Literal, OneOrMore, Suppress
# Define the unwanted sequence
hash_tag = Suppress(Literal('#{')) + CharsNotIn('}') + Suppress(Literal('}'))
text_part = CharsNotIn('#{')
# Combine the parts to match the entire string
parser = OneOrMore(Group(hash_tag) | text_part)
test_string = "Some text \n with a stranded # and a stranded { then a correct #{ insertion of \n some # other text } and then some text"

result = parser.searchString(test_string)
expected_result = ["Some text \n with a stranded # and a stranded { then a correct ",[" insertion of \n some # other text "]," and then some text"]
print(result)

The result is not the expected result (I get ["Some text \n with a stranded "])

• python
• pyparsing

Share Improve this question Follow edited Feb 11 at 22:48 TylerH 21.1k7777 gold badges7979 silver badges112112 bronze badges asked Feb 11 at 19:19 FoguxFogux 12799 bronze badges 1

• For a string templating program, look at using the transform_string method instead of search_string. The macro_expander.py script in the examples directory might give you some ideas also.. – PaulMcG Commented Feb 20 at 6:28

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1 Answer 1

Sorted by: Reset to default 0

I would use pyparsing's QuotedString class to define your template field, like this:

import pyparsing as pp

template_field = pp.QuotedString("#{", endQuoteChar="}", 
                                 escChar="\\", 
                                 multiline=True, 
                                 unquoteResults=True)
test_string = "Some text \n with a stranded # and a stranded { then a correct #{ insertion of \n some # other text } and then some text"

# just search for the template field
result = template_field.search_string(test_string)
expected_result = [[" insertion of \n some # other text "]]
print(result)
print(expected_result)

Since this is a templating kind of program, transform_string might do much of the search-and-replace work for you, if you can implement the transformation as a parse action:

# Using transform_string to transform the template_field
# (add some kind of transformation to the template_field using a parse action)
template_field.add_parse_action(lambda s, l, t: t[0].upper())
print(template_field.transform_string(test_string))

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