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Update Python_usage.rst

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Richard Berger
2020-10-02 17:19:51 -04:00
parent 60891fe6f9
commit 0475397229
1 changed files with 9 additions and 15 deletions
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doc/src/Python_usage.rst
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@ -356,9 +356,10 @@ against invalid accesses.
Retrieving or setting properties of LAMMPS objects
**************************************************
* :py:meth:`extract_compute() <lammps.lammps.extract_compute()>`
* :py:meth:`extract_fix() <lammps.lammps.extract_fix()>`
* :py:meth:`extract_variable() <lammps.lammps.extract_variable()>`
* :py:meth:`extract_compute() <lammps.lammps.extract_compute()>`: extract value(s) from a compute
* :py:meth:`extract_fix() <lammps.lammps.extract_fix()>`: extract value(s) from a fix
* :py:meth:`extract_variable() <lammps.lammps.extract_variable()>`: extract value(s) from a variable
* :py:meth:`set_variable() <lammps.lammps.set_variable()>`: set existing named string-style variable to value
.. code-block:: Python
@ -381,14 +382,6 @@ Retrieving or setting properties of LAMMPS objects
flag = lmp.set_variable(name,value) # set existing named string-style variable to value, flag = 0 if successful
For extract_atom(), a pointer to internal LAMMPS atom-based data is
returned, which you can use via normal Python subscripting. See the
extract() method in the src/atom.cpp file for a list of valid names.
Again, new names could easily be added if the property you want is not
listed. A pointer to a vector of doubles or integers, or a pointer to
an array of doubles (double \*\*) or integers (int \*\*) is returned. You
need to specify the appropriate data type via the type argument.
For extract_compute() and extract_fix(), the global, per-atom, or
local data calculated by the compute or fix can be accessed. What is
returned depends on whether the compute or fix calculates a scalar or
@ -405,7 +398,8 @@ data types. See the doc pages for individual :doc:`computes <compute>`
and :doc:`fixes <fix>` for a description of what they calculate and
store.
For extract_variable(), an :doc:`equal-style or atom-style variable <variable>` is evaluated and its result returned.
For extract_variable(), an :doc:`equal-style or atom-style variable <variable>`
is evaluated and its result returned.
For equal-style variables a single double value is returned and the
group argument is ignored. For atom-style variables, a vector of
@ -464,10 +458,10 @@ like this:
.. code-block:: Python
from ctypes import \*
from ctypes import *
natoms = lmp.get_natoms()
n3 = 3\*natoms
x = (n3\*c_double)()
n3 = 3*natoms
x = (n3*c_double)()
x[0] = x coord of atom with ID 1
x[1] = y coord of atom with ID 1
x[2] = z coord of atom with ID 1