On 19-10-15 07:12, Pietro wrote:
Dear Paulo,
On Sun, Oct 18, 2015 at 8:03 PM, Paulo van Breugel
<p.vanbreu...@gmail.com> wrote:
What would be the python equivalent of:
r.category mymap | r.category mymap rules=-
Let's split the problem in two step.
First capture the output of a module (the python equivalent of bash pipe):
{{{
from subprocess import PIPE # from the standard library import PIPE costant
from grass.pygrass.modules import Module # import the Module class from pygrass
rcat = Module('r.category', 'landuse', stdout_=PIPE) # use the spacial
parameter stdout_
rcat.outputs.stdout # the stdout is an attribute of the instanced class
'1\tdeveloped\n2\tagriculture\n3\therbaceous\n4\tshrubland\n5\tforest\n6\twater\n7\tsediment\n'
print(rcat.outputs.stdout)
1 developed
2 agriculture
3 herbaceous
4 shrubland
5 forest
6 water
7 sediment
}}}
Second provide a string as stdinput of a module:
{{{
Module('r.category', 'mymap', rules='-',
stdin_='1\tdeveloped\n2\tagriculture\n3\therbaceous\n4\tshrubland\n5\tforest\n6\twater\n7\tsediment\n')
Module('r.category')
}}}
or to do both things in one line:
{{{
Module('r.category', 'mymap', rules='-', stdin_=Module('r.category',
'landuse', stdout_=PIPE).outputs.stdout)
}}}
You can use a shourtcut to have a cleaner syntax close to bash:
{{{
from grass.pygrass.modules.shortcuts import raster as r
r.category('mymap', rules='-', stdin_=r.category('landuse',
stdout_=PIPE).outputs.stdout)
Module('r.category')
}}}
Dear Pietro, this is brilliant, thanks a lot!
There is an example in the documentation using r.colors but it is not
rendered corectly [0]
I tried out the examples on that page, but I couldn't get it all to
work. For example, there are some examples that use of "stdout_=PIPE"
and stdin_=PIPE. I though that might be what I was looking for, but
after trying (and failing) to run the examples I basically do not
understand what is done there. The solution you describe above is
actually more easy to intuitively understand. It would be a great
example to include on the manual page.
About the manual pages, although very detailed, they are sometimes a bit
hard to understand (perhaps mostly for non-programmers like me), and
could benefit from worked out examples like you provide above. I would
not mind providing input, but lack a proper understanding of the code.
On the other hand, I have had feedback with great examples /
explanations for two or three times now which I though would be great to
include in the manual. What is the best place for such feedback /
suggestions?
Have fun!
Pietro
[0]
https://grass.osgeo.org/grass71/manuals/libpython/pygrass.modules.interface.html#pygrass.modules.interface.module.Module
I had seen the example, but to be honest even after rereading it isn't
all clear to me
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