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Help with 'self' and 'set_usage'

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  Help with 'self' and 'set_usage' "L O'Shea" <lo0446@my.bristol.ac.uk> - 2013-07-09 10:03 -0700
    Re: Help with 'self' and 'set_usage' Ethan Furman <ethan@stoneleaf.us> - 2013-07-09 10:19 -0700
    Re: Help with 'self' and 'set_usage' Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-07-09 19:24 +0200
    Re: Help with 'self' and 'set_usage' Andrew Berg <robotsondrugs@gmail.com> - 2013-07-09 12:32 -0500
    Re: Help with 'self' and 'set_usage' "L O'Shea" <lo0446@my.bristol.ac.uk> - 2013-07-10 01:23 -0700

#50263 — Help with 'self' and 'set_usage'

Hi all,
I'm interning and have been given the job of extending a program that has been written by someone else. I've never used Python before so it's a bit of a struggle but I've got to say I'm loving the language so far.

In on of the scripts there is

def set_usage(self,s):
self.usage_str = s

Could anyone shed some light on this? I can't find mention of this anywhere in any Python documentation or anywhere else in the code where usage_str might be defined. Can you just create variables in that object by writing self.name = "david" self.hobby = "fishing"??

If this is any help it is used later in the program (or in other scripts) like

prog.set_usage("""%prog <command> [options] ....""")

Thanks for your help, I have spent a good while googling python docs, code snippets and reading through a Python book I have on my desk to no avail.

Cheers in advance.

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#50264

On 07/09/2013 10:03 AM, L O'Shea wrote:
>
> Hi all,

Howdy!

> I'm interning and have been given the job of extending a program that has been written by someone else. I've never used Python before so it's a bit of a struggle but I've got to say I'm loving the language so far.

Excellent way to start a question!  :)


> In one of the scripts there is
>
> def set_usage(self,s):
>     self.usage_str = s

Careful of whitespace when posting (I fixed that one for you).


> Can you just create variables in that object by writing self.name = "david" self.hobby = "fishing"??

Yup, you sure can.

--
~Ethan~

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#50265

Op 09-07-13 19:03, L O'Shea schreef:
> Hi all,
> I'm interning and have been given the job of extending a program that
> has been written by someone else. I've never used Python before so it's
> a bit of a struggle but I've got to say I'm loving the language so far.
>
> In on of the scripts there is
>
> def set_usage(self,s):
>     self.usage_str = s
>
> Could anyone shed some light on this? I can't find mention of this
> anywhere in any Python documentation or anywhere else in the code
> where usage_str might be defined. Can you just create variables in
> that object by writing self.name = "david" self.hobby = "fishing"??

Yes you can.

-- 
Antoon Pardon

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#50266

On 2013.07.09 12:03, L O'Shea wrote:
> Could anyone shed some light on this? I can't find mention of this anywhere in any Python documentation or anywhere else in the code where usage_str might be defined.
In Python, you don't declare or initialize variables before using them. In the example you gave, that is where usage_str is defined. You
simply assign an object to a name or attribute (which may or may not have existed previously). You can then change it to anything else you
want; Python is dynamically typed, so the object you assign to it can be of any type.

Note: a class with __slots__ defined is the exception to this, but that's a bit of an advanced topic.

BTW, you can play with objects in the interactive interpreter. It's a great way to quickly learn how certain things work.
-- 
CPython 3.3.2 | Windows NT 6.2.9200 / FreeBSD 9.1

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#50307

On Tuesday, 9 July 2013 18:03:41 UTC+1, L O'Shea  wrote:
> Hi all,
> 
> I'm interning and have been given the job of extending a program that has been written by someone else. I've never used Python before so it's a bit of a struggle but I've got to say I'm loving the language so far.
> 
> 
> 
> In on of the scripts there is
> 
> 
> 
> def set_usage(self,s):
> 
> self.usage_str = s
> 
> 
> 
> Could anyone shed some light on this? I can't find mention of this anywhere in any Python documentation or anywhere else in the code where usage_str might be defined. Can you just create variables in that object by writing self.name = "david" self.hobby = "fishing"??
> 
> 
> 
> If this is any help it is used later in the program (or in other scripts) like
> 
> 
> 
> prog.set_usage("""%prog <command> [options] ....""")
> 
> 
> 
> Thanks for your help, I have spent a good while googling python docs, code snippets and reading through a Python book I have on my desk to no avail.
> 
> 
> 
> Cheers in advance.

Thanks for the advice everyone that was really helpful! Gotta love the USA/UK time difference I can post a question here at the end of the day and it be answered by morning - Not that it took any of you very long!
Stay tuned for more Python questions :)

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