Question

I am trying to make a parser in python which can achieve two types of functionality

s1 = foo()
s2 = {'k1':v1,'k2':v2}
s3 = [v1,v2,v3...]

I say two types… where first type is usually objects and second types are kind off like variables.
Now First one is easy..

def parse_string_to_command(string):
     if "foo" in string:
         #handle this.
     elif # handle s2 
     elif #condition to handle s3

EDIT 1:
I think I didnt clearly stated what I am trying to achive.

All I am trying to do is follows:

Everything that passes from that function is a string.. some are methods.. while others are variables.
I am just trying to handle them accordingly.

Basically this is what user will be doing

 > params = {"input":"foobar"}
 > foo = Foo(params)

Now, to handle Foo method.. I do this:

   if "Foo" in string:
      tokens = string.split("=")
      # I have tokens [foo,Foo(params)]

   But params is a string now..whereas it is needed to be a dictionary.

Now I know i can just handle it here..inside Foo method.. but in general I want to handle these variable assignments inside parse_string_to_command function

Is it making any sense.

Answer 1

You might want to look into using pythons JSON parser for accomplishing your goal.

>>> import json
>>> a = json.loads('["foo", {"bar": ["baz", null, 1.0, 2]}]')
>>> a
[u'foo', {u'bar': [u'baz', None, 1.0, 2]}]
>>> a[0]
u'foo'
>>> a[1]
{u'bar': [u'baz', None, 1.0, 2]}
>>> a[1]['bar']
[u'baz', None, 1.0, 2]
>>>>>> a[1]['bar'][0]
u'baz'

or if you need it completely custom… with out the intention to write a complete parser for you, I imagine using some regular expressions will help make your job easier.

>>> import re
>>> s1 = "foo()"
>>> s2 = "{'k1':v1,'k2':v2}"
>>> s3 = "[v1,v2,v3]"
>>> re.match('(.*?)\(\)',s1).group(1)
'foo'
>>> re.findall('\{*(.*?):(.*?)[,\}$]+',s2)
[("'k1'", 'v1'), ("'k2'", 'v2')]
>>> re.findall('\[*(.*?)[,\]$]+',s3)
['v1', 'v2', 'v3']

To just identify the 3 types of input strings:

def parse_string_to_command(s):
    if re.match('(.*?\(\))',s):
        print "This is a function"
    elif re.match('^\{.*\}$',s):
        print "This is kind of like variables 1"
    elif re.match('^\[.*\]$',s):
        print "This is kind of like variables 2"