Name error in calling a function in python

Question

Why I am getting the error that is given below:

lhs_production = self.lhs()

NameError: global name 'self' is not defined

Below is the code that I have written:

class Grammar:
   def lhs(self):
      arrow_position = line.find('->')
      if arrow_position == -1:
         raise ValueError, 'No arrow position %s is found in %s' % (arrow_position, self.line)

      lhs_g = self.line[0:arrow_position].strip(' ')
      print "The Lhs for the line is: ", lhs_g

      check_space = re.search("\s", lhs, re.M)
      if check_space:
         raise ValueError, 'There is still some space in the lhs of the line'

      return self.lhs_g



def parse_line(line):
   if len(line) == 0:
      raise ValueError, 'No Line is found %s' % (line)
   lhs_production = self.lhs()
   rhs_predicates_production = rhs_predicates()
   pattern_list_production = pattern_list()
   return(lhs_production, rhs_predicates(), patterns())

Julian · Accepted Answer · 2012-07-24 21:54:27Z

2

Because self is not defined in the scope of that function :). Your indentation is off, you probably meant to make that a method (so indent all the lines) and then to add self as an argument, in which case the instance would take on the name self.

A few other things to look out for too, just by the by:

You should use if "->" in line: rather than .find() and checking if it's -1. For this, your first function seems to have a NameError, since line is not defined on its first line, not sure what you meant instead.
You should instantiate the exceptions, rather than making raise do it for you (so, raise ValueError("some stuff")
You can use if not line to check if it's a blank line.
return is a statement, not a function, so writing it like that is a bit confusing. Just use return lhs_production, bla, bla or put parens around that as long as there's a space there if you prefer.

Cheers :).

edited Jul 24, 2012 at 21:54

answered Jul 24, 2012 at 21:48

Julian

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matzahboy · Accepted Answer · 2012-07-24 21:48:52Z

0

self is not a global variable. It is passed in to class methods. The parse_line function is a global scope function, not a class method. Therefore, self does not exist in the scope of that function.

Any method that uses self needs to take self in as a parameter.

answered Jul 24, 2012 at 21:48

matzahboy

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Silas Ray · Accepted Answer · 2012-07-24 21:48:55Z

0

There is no self in that context, unless your indentation is wrong. You need to reference an instance of the object to call a method when outside of the object's scope. self is really just a label anyway; it only has special meaning by convention. You need a grammar=Grammar() somewhere in there.

answered Jul 24, 2012 at 21:48

Silas Ray

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