update a pandas dataset, using pandas.eval or df.apply - pandas

Question

I have a pandas dataframe with a lot rows.
One of the columns, lets say WHERE_CLAUSE has some sql like conditions. So I created a new column which uses these conditions and translates it to python/pandas statements.
Eg: column 'WHERE_CLAUSE' has the value for a row like 'ACCOUNTING_PERIOD NOT IN (999)' , I am translating it to a pandas statement in a new column 'EVAL_EXPR' with value '''base_table.loc[(base_table.ACCOUNTING_PERIOD.isin([999]),"REPORT_TYPE_ID")] = "initial"'''.
Now this is a perfectly valid statement if I execute it directly and it does update the dataset.
The problem I face is, since it's a string, I am using
pandas.eval which has the above value and it fails
So this is what I tried:
eval_str ='''base_table.loc[(base_table.ACCOUNTING_PERIOD.isin([999]),"REPORT_TYPE_ID")] = "initial"'''
print(eval_str)
pd.eval(eval_str)
and this is the error I receive:
> base_table["REPORT_TYPE_ID"].apply(lambda x: "final" if
> base_table.ACCOUNTING_PERIOD.isin([999]))
>
> Traceback (most recent call last):
>
> File "C:\ProgramData\Anaconda3\lib\site-
> packages\IPython\core\interactiveshell.py", line 3331, in run_code
> exec(code_obj, self.user_global_ns, self.user_ns)
>
> File "<ipython-input-31-96405158714d>", line 9, in <module>
> pd.eval(eval_str)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\eval.py",
> line 332, in eval
> parsed_expr = Expr(expr, engine=engine, parser=parser, env=env)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 764, in __init__
> self.terms = self.parse()
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 781, in parse
> return self._visitor.visit(self.expr)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 375, in visit
> return visitor(node, **kwargs)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 381, in visit_Module
> return self.visit(expr, **kwargs)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 375, in visit
> return visitor(node, **kwargs)
>
> File
> "C:\ProgramData\Anaconda3\lib\site-packages\pandas\core\computation\expr.py",
> line 583, in visit_Assign
> raise SyntaxError("left hand side of an assignment must be a single name")
>
> File "<string>", line unknown SyntaxError: left hand side of an
> assignment must be a single name
I know pandas.apply doesn't take statements but expressions which is obviously what I am trying to execute. But how do I fix this?
I dont know how to tweak this ,so that I can use dataframe['column'].apply to avoid this issue.
Any suggestions much appreciated.

Answer 1

So to execute a dynamically generated python statement, I used this function 'exec'.It worked like charm!
Code Tried:
eval_str = '''base_table.loc[(base_table.ACCOUNTING_PERIOD.isin([999]),"REPORT_TYPE_ID")] = "initial"'''
exec(eval_Str)
Reference:
It was already answered in stackoverflow. Evaluating dynamically generated statements in Python