run a string as code?

[py_genetic]

How can you make python interpret a string (of py code) as code. For
example if you want a py program to modify itself as it runs. I know
this is an advantage of interpreted languages, how is this done in
python. Thanks.

[mtbeedee@gmail.com]

Re: run a string as code?

py_genetic wrote:

How can you make python interpret a string (of py code) as code. For
example if you want a py program to modify itself as it runs. I know
this is an advantage of interpreted languages, how is this done in
python. Thanks.

This might do it...

>>print eval.__doc__

eval(source[, globals[, locals]]) -value

Evaluate the source in the context of globals and locals.
The source may be a string representing a Python expression
or a code object as returned by compile().
The globals must be a dictionary and locals can be any mappping,
defaulting to the current globals and locals.
If only globals is given, locals defaults to it.

[py_genetic]

Re: run a string as code?


mtbeedee@gmail. com wrote:

py_genetic wrote:

How can you make python interpret a string (of py code) as code. For
example if you want a py program to modify itself as it runs. I know
this is an advantage of interpreted languages, how is this done in
python. Thanks.

>
This might do it...
>

>print eval.__doc__

eval(source[, globals[, locals]]) -value
>
Evaluate the source in the context of globals and locals.
The source may be a string representing a Python expression
or a code object as returned by compile().
The globals must be a dictionary and locals can be any mappping,
defaulting to the current globals and locals.
If only globals is given, locals defaults to it.

For example each time this line is interpreted I would like to use the
new value of the state var which is a global var. How can I force
state to be identified and used in this string.

r_table = h5file.root.sta te_raw_records. neg_records

r_table = eval("h5file.ro ot.state_raw_re cords.neg_recor ds") ??
r_table = h5file.root.eva l("state")_raw_ records.neg_rec ords ?? eval is
not a part of root

dont think either of these is very logical? Any ideas? Possibly the
parser mod?

[py_genetic]

Re: run a string as code?


py_genetic wrote:

mtbeedee@gmail. com wrote:

py_genetic wrote:

How can you make python interpret a string (of py code) as code. For
example if you want a py program to modify itself as it runs. I know
this is an advantage of interpreted languages, how is this done in
python. Thanks.

This might do it...

>>print eval.__doc__

eval(source[, globals[, locals]]) -value

Evaluate the source in the context of globals and locals.
The source may be a string representing a Python expression
or a code object as returned by compile().
The globals must be a dictionary and locals can be any mappping,
defaulting to the current globals and locals.
If only globals is given, locals defaults to it.

>
For example each time this line is interpreted I would like to use the
new value of the state var which is a global var. How can I force
state to be identified and used in this string.
>
r_table = h5file.root.sta te_raw_records. neg_records
>
r_table = eval("h5file.ro ot.state_raw_re cords.neg_recor ds") ??
r_table = h5file.root.eva l("state")_raw_ records.neg_rec ords ?? eval is
not a part of root
>
dont think either of these is very logical? Any ideas? Possibly the
parser mod?

Got it!

tmp = "h5file.root."+ state+"_raw_rec ords.pos_record s"
r_table = eval(tmp)

works great thanks for the help!

[Gary Herron]

Re: run a string as code?

py_genetic wrote:

py_genetic wrote:
>

>mtbeedee@gmail. com wrote:
>>

>>py_genetic wrote:
>>>
>>>How can you make python interpret a string (of py code) as code. For
>>>example if you want a py program to modify itself as it runs. I know
>>>this is an advantage of interpreted languages, how is this done in
>>>python. Thanks.
>>>>
>>This might do it...
>>>
>>>
>>>>>print eval.__doc__
>>>>>>
>>eval(source[, globals[, locals]]) -value
>>>
>>Evaluate the source in the context of globals and locals.
>>The source may be a string representing a Python expression
>>or a code object as returned by compile().
>>The globals must be a dictionary and locals can be any mappping,
>>defaulting to the current globals and locals.
>>If only globals is given, locals defaults to it.
>>>

>For example each time this line is interpreted I would like to use the
>new value of the state var which is a global var. How can I force
>state to be identified and used in this string.
>>
>r_table = h5file.root.sta te_raw_records. neg_records
>>
>r_table = eval("h5file.ro ot.state_raw_re cords.neg_recor ds") ??
>r_table = h5file.root.eva l("state")_raw_ records.neg_rec ords ?? eval is
>not a part of root
>>
>dont think either of these is very logical? Any ideas? Possibly the
>parser mod?
>>

>
Got it!
>
tmp = "h5file.root."+ state+"_raw_rec ords.pos_record s"
r_table = eval(tmp)
>
works great thanks for the help!
>

Yes, it works, but this is not a good place to use eval. Now that we see
how you want to use it, we can find a *much* better way to do it.

If you want to lookup an attribute of an object, but the attribute name
is a string in a variable, then use getattr to do the lookup.

If in interpret your code correctly:

attrname = state + "_raw_recor ds"
obj = getattr(h5file. root, attrname)
r_table = obj.pos_records

These, of course, could be combined into a single (but not necessarily
clearer) line.

Gary Herron

[py_genetic]

Re: run a string as code?

Gary Herron wrote:

py_genetic wrote:

py_genetic wrote:

mtbeedee@gmail. com wrote:
>
>py_genetic wrote:
>>
>>How can you make python interpret a string (of py code) as code. For
>>example if you want a py program to modify itself as it runs. I know
>>this is an advantage of interpreted languages, how is this done in
>>python. Thanks.
>>>
>This might do it...
>>
>>
>>>>print eval.__doc__
>>>>>
>eval(source[, globals[, locals]]) -value
>>
>Evaluate the source in the context of globals and locals.
>The source may be a string representing a Python expression
>or a code object as returned by compile().
>The globals must be a dictionary and locals can be any mappping,
>defaulting to the current globals and locals.
>If only globals is given, locals defaults to it.
>>
For example each time this line is interpreted I would like to use the
new value of the state var which is a global var. How can I force
state to be identified and used in this string.
>
r_table = h5file.root.sta te_raw_records. neg_records
>
r_table = eval("h5file.ro ot.state_raw_re cords.neg_recor ds") ??
r_table = h5file.root.eva l("state")_raw_ records.neg_rec ords ?? eval is
not a part of root
>
dont think either of these is very logical? Any ideas? Possibly the
parser mod?
>

Got it!

tmp = "h5file.root."+ state+"_raw_rec ords.pos_record s"
r_table = eval(tmp)

works great thanks for the help!

Yes, it works, but this is not a good place to use eval. Now that we see
how you want to use it, we can find a *much* better way to do it.
>
If you want to lookup an attribute of an object, but the attribute name
is a string in a variable, then use getattr to do the lookup.
>
If in interpret your code correctly:
>
attrname = state + "_raw_recor ds"
obj = getattr(h5file. root, attrname)
r_table = obj.pos_records
>
These, of course, could be combined into a single (but not necessarily
clearer) line.
>
Gary Herron

So it is eval() is more appropriate when evalution blocks of string
code, and getattr() is more efficient for dealing with objects such as
h5file object above? Thanks.