Re: [Pyparsing] Check for tabs

[Paul M. <pt...@au...>]

One of pyparsing's default behaviors is to skip over whitespace, so when
whitespace is part of your parser, you sometimes have to take some extra
steps.

In the case of <TAB>s, you need to override pyparsing's default of replacing
tabs in the input string with spaces. Otherwise, the input string first gets
run through str.expandtabs before being parsed, and the tab expressions in
your grammar will never match. Here's how:


word = Word(alphas)
tab = White('\t', exact=1)

data = word + tab + word + tab + tab + word

# this step is important
data.parseWithTabs()

s = 'name\tdate\t\tlocation'
data.parseString(s).asList()
['name', '\t', 'date', '\t', '\t', 'location']


If you leave out this call, you'll get a ParseException because your input
string will have been expanded to 'name    date            location', with
no tabs.

-- Paul



-----Original Message-----
From: Hanchel Cheng [mailto:han...@br...] 
Sent: Monday, October 28, 2013 3:52 PM
To: pyp...@li...
Subject: [Pyparsing] Check for tabs

Hello!

I'm new to pyparsing and relatively new to Python as well. I'm really
astounded by the multitude of functionality that pyparsing has.
My question is pretty basic:
I have a string 'name\tdate\t\tlocation'.
What would I do to ensure that between the 'name' and 'date' there is
exactly one tab and between 'date' and 'location' there is exactly two tabs?

Thanks,
Hanchel
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