有没有办法在python脚本中获取所有变量值？

Question

If this question is out of scope, please suggest where I can move it.

I am having a lot of python (version 2.7) scripts, which are invoking each other. To get a view of which script calls which, I have currently built a nice GUI tree that maps this.

The problem I have lies within parsing the files. The simplest example of a script invoking another script is calling:

os.system('another.py')

This is trivial to parse, just take what is inside the parenthesis. I have now come to evaluating variables. My current way of evaluating variables works like this:

x = 'another'
dot = '.'
py = 'py'
os.system(x+dot+py) # Find three variables

listOfVars = getVarsBetweenParenthesis() # Pseudo code.

# Call getVarValue to find value for every variable, then add these together 

'''
    Finds the value of a variable.
'''
def getVarValue(data, variable, stop):
    match = ''
    for line in data:
        noString = line.replace(' ', '') # Remove spaces
        if variable+'=' in noString:
            match = line.replace(variable+'=', '').strip()
        if line == stop:
            break
    return match

Aside from being an ugly hack, this code has its disadvantages. When doing the Call getVarValue to find value for every variable, then add these together not all variables get their desired value. For instance:

x = os.getcwd() # Cannot be found by getVarValue
script = 'x.py'
os.system(x+script) # Find three variables

The problem is that I do not want to invoke these scripts (some scripts create/updates files), but rather parse them by value. Since the python interpreter is able to parse scripts I figure that this must be possible.

I have already looked in to tokenize , which gave me little help, and abstract syntax trees . However, both of these do not seem to be able to parse variables without running the file.

Is there a way (preferably pythonic) to retrieve a variable value without executing the script?

Answer 1

Modified from this Python3 Q&A, here is an example of using the ast module to extract a variable.

It could be modified to extract all variables, but ast.literal_eval can only evaluate simple types.

def safe_eval_var_from_file(mod_path, variable, default=None, raise_exception=False):
    import ast
    ModuleType = type(ast)
    with open(mod_path, "r") as file_mod:
        data = file_mod.read()

    try:
        ast_data = ast.parse(data, filename=mod_path)
    except:
        if raise_exception:
            raise
        print("Syntax error 'ast.parse' can't read %r" % mod_path)
        import traceback
        traceback.print_exc()

    if ast_data:
        for body in ast_data.body:
            if body.__class__ == ast.Assign:
                if len(body.targets) == 1:
                    print(body.targets[0])
                    if getattr(body.targets[0], "id", "") == variable:
                        try:
                            return ast.literal_eval(body.value)
                        except:
                            if raise_exception:
                                raise
                            print("AST error parsing %r for %r" % (variable, mod_path))
                            import traceback
                            traceback.print_exc()
    return default

# example use
this_variable = {"Hello": 1.5, 'World': [1, 2, 3]}
that_variable = safe_eval_var_from_file(__file__, "this_variable")
print(this_variable)
print(that_variable)