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I've got a variable in a loop that I'm trying to expand/translate/
readdress as an existing dict so as to add some keys into it..

eg; I have a set of existing dicts: dictFoo, dictBar, dictFrotz (names
changed to protect the innocent)

now I'd like to check them all for the existence of certain default
keys; ie, if the dicts don't contain the keys, add them in with
default values.

so, I've got:

for a in ['dictFoo','dictBar','dictFrotz']:
if hasattr(a,'srcdir') == False:
a['srcdir']='/usr/src'

the error I get (which I expect) is 'str' object doesn't support item
assignment.

what incantation do I cast on 'a' to make the interpreter parse it as
'dictFoo' on the first iteration, 'dictBar' on the second, and so
forth?

and/or less importantly, what is such a transformation called, to help
me target my searching?

thanks

On Apr 3, 10:56*pm, idle <spiro.har...@gmail.com> wrote:
> I've got a variable in a loop that I'm trying to expand/translate/
> readdress as an existing dict so as to add some keys into it..
>
> eg; I have a set of existing dicts: dictFoo, dictBar, dictFrotz (names
> changed to protect the innocent)
>
> now I'd like to check them all for the existence of certain default
> keys; ie, if the dicts don't contain the keys, add them in with
> default values.
>
> so, I've got:
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> * * if hasattr(a,'srcdir') == False:
> * * * * a['srcdir']='/usr/src'
>
> the error I get (which I expect) is 'str' object doesn't support item
> assignment.
>
> what incantation do I cast on 'a' to make the interpreter parse it as
> 'dictFoo' on the first iteration, 'dictBar' on the second, and so
> forth?
>
> and/or less importantly, what is such a transformation called, to help
> me target my searching?
>
> thanks

You want a to iterate through the dictionary *objects*, not *names*,
so write

for a in [dictFoo, dictBar, dictFrotz]:
...

BTW, hasattr() is not what you want as it check the existence of an
attribute, i.e. a.hasattr('x') means that a.x exists; you could write
the whole thing as:

for a in dictFoo, dictBar, dictFrotz:
if 'srcdir' not in a:
a['srcdir'] = '/usr/src'

Or more concisely:

for a in ... :
a.setdefault('srcdir', '/usr/src')


For more information, help(dict) is your friend

HTH

--
Arnaud

idle wrote:
> I've got a variable in a loop that I'm trying to expand/translate/
> readdress as an existing dict so as to add some keys into it..
>
> eg; I have a set of existing dicts: dictFoo, dictBar, dictFrotz (names
> changed to protect the innocent)
>
> now I'd like to check them all for the existence of certain default
> keys; ie, if the dicts don't contain the keys, add them in with
> default values.
>
> so, I've got:
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> if hasattr(a,'srcdir') == False:
> a['srcdir']='/usr/src'
>
> the error I get (which I expect) is 'str' object doesn't support item
> assignment.
>
> what incantation do I cast on 'a' to make the interpreter parse it as
> 'dictFoo' on the first iteration, 'dictBar' on the second, and so
> forth?
>
> and/or less importantly, what is such a transformation called, to help
> me target my searching?
>
> thanks
>

Try this:

for a in [dictFoo, dictBar, dictFrotz]:
if 'srcdir' in a:
a['srcdir']='/usr/src'

Gary Herron

On Apr 4, 8:56 am, idle <spiro.har...@gmail.com> wrote:
> I've got a variable in a loop that I'm trying to expand/translate/
> readdress as an existing dict so as to add some keys into it..
>
> eg; I have a set of existing dicts: dictFoo, dictBar, dictFrotz (names
> changed to protect the innocent)
>
> now I'd like to check them all for the existence of certain default
> keys; ie, if the dicts don't contain the keys, add them in with
> default values.
>
> so, I've got:
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> if hasattr(a,'srcdir') == False:
> a['srcdir']='/usr/src'
>
> the error I get (which I expect) is 'str' object doesn't support item
> assignment.
>
> what incantation do I cast on 'a' to make the interpreter parse it as
> 'dictFoo' on the first iteration, 'dictBar' on the second, and so
> forth?
>
> and/or less importantly, what is such a transformation called, to help
> me target my searching?
>

It's called "deleting extraneous apostrophes from source code".

Happy googling!

brilliant.

thanks to both of you.

idle wrote:
> brilliant.
>
Hardly. Any perceived brilliance is in the design of Python, not our
simple and hopefully effective use of it.

Gary Herron


> thanks to both of you.
>

idle skrev:

> now I'd like to check them all for the existence of certain default
> keys; ie, if the dicts don't contain the keys, add them in with
> default values.
>
> so, I've got:
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> if hasattr(a,'srcdir') == False:
> a['srcdir']='/usr/src'

There are a few ways to do it.

for a in ['dictFoo','dictBar','dictFrotz']:
if not a.has_key('srcdir'):
a['srcdir'] = '/usr/src'

for a in ['dictFoo','dictBar','dictFrotz']:
if not 'srcdir' in a:
a['srcdir'] = '/usr/src'

for a in ['dictFoo','dictBar','dictFrotz']:
a.setdefault('srcdir') = '/usr/src'


--

hilsen/regards Max M, Denmark

http://www.mxm.dk/
IT's Mad Science

On Apr 4, 9:44 am, Max M <m...@mxm.dk> wrote:
> idle skrev:
>
> > now I'd like to check them all for the existence of certain default
> > keys; ie, if the dicts don't contain the keys, add them in with
> > default values.
>
> > so, I've got:
>
> > for a in ['dictFoo','dictBar','dictFrotz']:
> > if hasattr(a,'srcdir') == False:
> > a['srcdir']='/usr/src'
>
> There are a few ways to do it.
>
> for a in ['dictFoo','dictBar','dictFrotz']:

Ummm ... excessive apostrophes plus bonus gross syntax error, dood.
Did you try running any of these snippets???

> if not a.has_key('srcdir'):

a is a str object. Bang.


> a['srcdir'] = '/usr/src'
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> if not 'srcdir' in a:
> a['srcdir'] = '/usr/src'

a is a str object. Bang.
>
> for a in ['dictFoo','dictBar','dictFrotz']:
> a.setdefault('srcdir') = '/usr/src'

SyntaxError: can't assign to function call

>
> --
>
> hilsen/regards Max M, Denmark
>
> http://www.mxm.dk/
> IT's Mad Science

Sure is.

John Machin skrev:
> On Apr 4, 9:44 am, Max M <m...@mxm.dk> wrote:


> Ummm ... excessive apostrophes plus bonus gross syntax error, dood.
> Did you try running any of these snippets???

No I just wanted to quickly show different ways to do it.

The dicts in the original question wasn't dicts either. So I asumed I
could answer in the same vein.



>> http://www.mxm.dk/
>> IT's Mad Science
>
> Sure is.

Oh yes. That will motivate further answers.


--

hilsen/regards Max M, Denmark

http://www.mxm.dk/
IT's Mad Science