Hi, Thanks a lot for the clarification. Regards, Lusine Atanesyan 2014-11-27 8:01 GMT+04:00 Zachary Ware :

Hi Lusine,

First, I'd like to note that this is not the correct list for reporting bugs with Python itself; this list is for discussion of Python's documentation. That being said...

On Wed, Nov 26, 2014 at 1:32 PM, Lusine Atanesyan wrote:

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Hi,

I found a pyhton bug. Here is the description:

Summary: It is impossible to change tuple to list.

Overview description. It is impossible to change tuple to list when there is a independent list with the "list" name.

Steps to reproduce: >>> list = [1, 2, 3] >>> tup = (5, 6, 7) >>> list(tup)

Actual result: The following error is generated: Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'list' object is not callable

This is the expected result. By using the name "list" for a list object, you are shadowing the built-in name "list", which is the name of the list object constructor. Python's name resolution algorithm first checks for a local name, followed by a global name if no local is found, followed by a built-in name (a member of the builtins (or __builtin__ in Python2) module). Since executing "list = [1,2,3]" creates a local name "list", it is found before the built-in name "list"; list objects are not callable, hence the error you got. Note that it doesn't actually matter what you define the local name "list" to be:

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list = "this is not a list" tup = (4,5,6) list(tup) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'str' object is not callable

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Expect result: Either it should be possible to change the tuple to list or the error should generated when creating a list with the "list" name.

Name shadowing can be a very useful feature, allowing things like (in Python 3) redefining the name "print" to be a wrapper around "log.debug", so it's not going away. The real solution here is to either just not use the name "list" in a local scope (a lot of people use "lst" or "list_" or just "l" if your font distinguishes between "l" and "I" properly), or to import builtins (or __builtin__ in Python 2) and use "builtins.list" instead of just "list" when you need the built-in list. It's also possible to do something extraordinarily ugly like "type([])(tup)", but that's just going a little too far :)

Hope this helps, -- Zach