Importing a python module without actually executing it

Question

In the context of a complex application, I need to import user-supplied \'scripts\'. Ideally, a script would have

def init():
    blah

def execute():
    mo         


        

Answer 1

Not sure if you'll consider this elegant, but it is somewhat intelligent in the sense that it recognizes when def init are tokens and not just part of a tricky multi-line string:

'''
def init does not define init...
'''

It will not recognize when init is defined in tricky alternate ways such as

init = lambda ...

or

codestr='def  i'+'nit ...'
exec(codestr)

The only way to handle all such cases is to run the code (e.g. in a sandbox or by importing) and inspect the result.

---

import tokenize
import token
import io
import collections

userscript = '''\
def init():
    blah

"""
def execute():
    more blah
"""

yadda
'''

class Token(object):
    def __init__(self, tok):
        toknum, tokval, (srow, scol), (erow, ecol), line = tok
        self.toknum = toknum
        self.tokname = token.tok_name[toknum]
        self.tokval = tokval
        self.srow = srow
        self.scol = scol
        self.erow = erow
        self.ecol = ecol
        self.line = line    

class Validator(object):
    def __init__(self, codestr):
        self.codestr = codestr
        self.toks = collections.deque(maxlen = 2)
        self.names = set()
    def validate(self):
        tokens = tokenize.generate_tokens(io.StringIO(self.codestr).readline)
        self.toks.append(Token(next(tokens)))
        for tok in tokens:
            self.toks.append(Token(tok))            
            if (self.toks[0].tokname == 'NAME'     # First token is a name
                and self.toks[0].scol == 0         # First token starts at col 0
                and self.toks[0].tokval == 'def'   # First token is 'def'
                and self.toks[1].tokname == 'NAME' # Next token is a name
                ):
                self.names.add(self.toks[1].tokval)
        delta = set(['init', 'cleanup', 'execute']) - self.names
        if delta:
            raise ValueError('{n} not defined'.format(n = ' and '.join(delta)))

v = Validator(userscript)
v.validate()

yields

ValueError: execute and cleanup not defined