472,958 Members | 2,215 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 472,958 software developers and data experts.

Re: why? __builtins__ key added from eval

On Tue, 30 Sep 2008 16:04:34 -0500, William Purcell wrote:
I want to use eval to evaluate wx.TextCtrl inputs. How can I keep python
from adding the __builtins__ key to mydict when I use it with eval?
Other wise I have to __delitem__('__builtins__') everytime I use eval?
>>>mydict = {'a':2,'b':3}
{'a': 2, '__builtins__': {'IndexError': <type 'exceptions.IndexError'>,
...(I'll spare you the rest)...}, 'b': 3}

Also, how come eval has this behavior? Is it desirable?

when you pass mydict, it is used as the global variables in the eval,
right? Then, you passed a code to eval('...', mydict), sometimes you
might create global variable inside eval, and you want to see the value
of that inner global, that's why python modified mydict as a side-effect.

Then what is __builtins__ doing there? Because when eval created an
environment for the code to run, python interpreter need to define things
that it used by itself. The __builtins__ contained all built-in names
that is always available in python (python have to store it somewhere,
the built-in names couldn't be bound by magic, right?).

You could remove the builtin if you don't think it is necessary for you.
Or you could do "dictionary comprehension" that collects only names you
require (actually use generator comprehension then do a dict()
conversion, dictionary comprehension was rejected some time ago)

newdict = dict(k, v for k, v in mydict.iteritems() if k in ['a', 'b'])

or you could make a copy of mydict before passing it to eval.

Last note: eval is evil. (no pun intended)

Oct 2 '08 #1
0 1175

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: Opinder | last post by:
Hi, For the Python experts out there: Are there any side effects in assigning new variables to the __builtins__ module for the purpose of exposing variables to imported modules. For...
by: Mathieu Fenniak | last post by:
Good day, I'm writing an application which creates modules and runs Python code on the fly, embedding Python. The main function of the code is loaded into the __main__ module: (Error checking...
by: Matteo Merli | last post by:
Hi, is there a way to save objects in the __builtins__ namespace? the goal is to make them available in all the modules of my app, without reimporting all the things and keep references... The...
by: Michael Hohn | last post by:
Hi, using the file builtin_check.py with content # Module builtin_check # Inconstency in the binding of __builtins__ def get_binding(name): return locals() def get_global_binding(name):
by: Collin Winter | last post by:
Hallo all, As it currently stands, the type of the global __builtins__ differs depending on whether you're in the __main__ namespace (__builtins__ is a module) or not (its a dict). I was...
by: Adam Hupp | last post by:
I've noticed some unexpected behavior with __builtins__ during module import. It seems that during module import __builtins__ is a dict but at all other times it is a module. For example, if...
by: loquehumaine | last post by:
Hi there, I'm a newby in python (I know a little in programmation) and I have a lot of questions on builtins but my first one is about modules... I have seen that if I type help() at a prompt,...
by: Patrick Maupin | last post by:
__builtins__ in 2.5.2 doesn't seem to behave like I remember it did the last time I did some custom stuff with it, a very long time ago. This isn't surprising, because of ongoing optimization,...
by: Gabriel Genellina | last post by:
En Sun, 07 Sep 2008 14:00:48 -0300, Patrick Maupin <pmaupin@gmail.comescribió: Python takes some shortcuts when dealing with builtins. I'll just describe what happens (I won't say whether it is...
by: DJRhino | last post by:
Was curious if anyone else was having this same issue or not.... I was just Up/Down graded to windows 11 and now my access combo boxes are not acting right. With win 10 I could start typing...
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 4 Oct 2023 starting at 18:00 UK time (6PM UTC+1) and finishing at about 19:15 (7.15PM) The start time is equivalent to 19:00 (7PM) in Central...
by: Aliciasmith | last post by:
In an age dominated by smartphones, having a mobile app for your business is no longer an option; it's a necessity. Whether you're a startup or an established enterprise, finding the right mobile app...
by: tracyyun | last post by:
Hello everyone, I have a question and would like some advice on network connectivity. I have one computer connected to my router via WiFi, but I have two other computers that I want to be able to...
by: NeoPa | last post by:
Hello everyone. I find myself stuck trying to find the VBA way to get Access to create a PDF of the currently-selected (and open) object (Form or Report). I know it can be done by selecting :...
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 1 Nov 2023 starting at 18:00 UK time (6PM UTC) and finishing at about 19:15 (7.15PM) Please note that the UK and Europe revert to winter time on...
by: nia12 | last post by:
Hi there, I am very new to Access so apologies if any of this is obvious/not clear. I am creating a data collection tool for health care employees to complete. It consists of a number of...
by: NeoPa | last post by:
Introduction For this article I'll be focusing on the Report (clsReport) class. This simply handles making the calling Form invisible until all of the Reports opened by it have been closed, when it...
by: GKJR | last post by:
Does anyone have a recommendation to build a standalone application to replace an Access database? I have my bookkeeping software I developed in Access that I would like to make available to other...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.