how to use pyparsing for identifiers that start with a constant string

[Guest]

I am scanning text that has identifiers with a constant prefix string
followed by alphanumerics and underscores. I can't figure out, using
pyparsing, how to match for this. The example expression below seems to
be looking for whitespace between the 'atod' and the rest of the
identifier.

identifier_atod = 'atod' + pp.Word('_' + pp.alphanums)

How can I get pyparsing to match 'atodkj45k' and 'atod_asdfaw', but not
'atgdkasdjfhlksj' and 'atod asdf4er', where the first four characters
must be 'atod', and not followed by whitespace?

Thanks!

 

[Kent Johnson]

I am scanning text that has identifiers with a constant prefix string
followed by alphanumerics and underscores. I can't figure out, using
pyparsing, how to match for this. The example expression below seems to
be looking for whitespace between the 'atod' and the rest of the
identifier.

identifier_atod = 'atod' + pp.Word('_' + pp.alphanums)

How can I get pyparsing to match 'atodkj45k' and 'atod_asdfaw', but not
'atgdkasdjfhlksj' and 'atod asdf4er', where the first four characters
must be 'atod', and not followed by whitespace?

Here is one way using pyparsing.Combine:

>>> from pyparsing import *
>>> tests = [ 'atodkj45k', 'atod_asdfaw', 'atgdkasdjfhlksj', 'atod asdf4er']
>>> ident = Combine(Literal('atod') + Word('_' + alphanums))
>>> for t in tests:

... try:
... print ident.parseString(t)
... except:
... print 'No match', t
...
['atodkj45k']
['atod_asdfaw']
No match atgdkasdjfhlksj
No match atod asdf4er
Kent

 

[Paul McGuire]

Be careful, Kent. You may get tagged as "the new pyparsing guy."

-- Paul

 

[Kent Johnson]

Be careful, Kent. You may get tagged as "the new pyparsing guy."

Yeah, I was a little surprised I beat you to that one

Kent