PyMAPDL Language and Usage¶
This section gives you an overview of the PyMAPDL API for the
Mapdl class. For additional reference, see Mapdl.
Overview¶
When calling MAPDL commands as functions, each command has been
translated from its original MAPDL all CAPS format to a PEP8
compatible format. For example, ESEL is now Mapdl.esel(). Additionally, MAPDL commands
containing a / or * have had those characters removed, unless
this causes a conflict with an existing name. Most notable is
/SOLU which would conflict with SOLU. Therefore, the
/SOLU has been renamed to Mapdl.slashsolu() to differentiate it from solu.
Out of the 1500 MAPDL commands, about 15 start with slash and 8
with star.
MAPDL commands that normally have an empty space, such as ESEL, S,
TYPE, , 1 should include an empty string when called by Python:
mapdl.esel('s', 'type', '', 1)
or these commands can be called using keyword arguments:
mapdl.esel('s', 'type', vmin=1)
None of these restrictions apply to commands run with Mapdl.run(), and it may be easier to run some of
these commands (e.g. "/SOLU"):
mapdl.run('/SOLU')
mapdl.solve()
You can use the alternative:
mapdl.slashsolu()
Some commands can only be run non-interactively from within in a
script. PyMAPDL gets around this restriction by writing the commands
to a temporary input file and then reading the input file. To run a
group of commands that must be run non-interactively, set the
mapdl to run a series of commands as an input file by using
Mapdl.non_interactive()
as in this example:
with mapdl.non_interactive:
mapdl.run("*VWRITE,LABEL(1),VALUE(1,1),VALUE(1,2),VALUE(1,3)")
mapdl.run("(1X,A8,' ',F10.1,' ',F10.1,' ',1F5.3)")
Also note that macros created within PyMAPDL (rather than loaded from
a file) do not appear to run correctly. For example, the macro
DISP created using the *CREATE command within APDL:
! SELECT NODES AT Z = 10 TO APPLY DISPLACEMENT
*CREATE,DISP
NSEL,R,LOC,Z,10
D,ALL,UZ,ARG1
NSEL,ALL
/OUT,SCRATCH
SOLVE
*END
! Call the function
*USE,DISP,-.032
*USE,DISP,-.05
*USE,DISP,-.1
Should be written as:
def DISP(ARG1='', ARG2='', ARG3='', ARG4='', ARG5='', ARG6='',
ARG7='', ARG8='', ARG9='', ARG10='', ARG11='', ARG12='',
ARG13='', ARG14='', ARG15='', ARG16='', ARG17='', ARG18=''):
mapdl.nsel("R", "LOC", "Z", 10) #SELECT NODES AT Z = 10 TO APPLY DISPLACEMENT
mapdl.d("ALL", "UZ", ARG1)
mapdl.nsel("ALL")
mapdl.run("/OUT,SCRATCH")
mapdl.solve()
DISP(-.032)
DISP(-.05)
DISP(-.1)
If you have an existing input file with a macro, it can be converted
using convert_script()
setting macros_as_functions=True:
>>> from ansys.mapdl import core as pymapdl
>>> pymapdl.convert_script(apdl_inputfile, pyscript, macros_as_functions=True)
Additional Options When Running Commands¶
Commands can be run in mute or verbose mode, which allows you
to suppress or print the output in as it is being run for any MAPDL
command. This can be especially helpful for long-running commands
like SOLVE. This works for the pythonic wrapping of all commands
and when using Mapdl.run().
Run a command and suppress its output:
>>> mapdl.run('/PREP7', mute=True)
>>> mapdl.prep7(mute=True)
Run a command and stream its output while it is being run.
>>> mapdl.run('SOLVE', mute=True)
>>> mapdl.solve(verbose=True)
Note
The verbose and mute features are only available when
running MAPDL in gRPC mode.
Running Several Commands or an Input File¶
You can run several MAPDL commands as a unified block using
Mapdl.run_multiline().
This is useful when using PyMAPDL with older MAPDL scripts. For
example:
>>> cmd = '''/prep7
! Mat
MP,EX,1,200000
MP,NUXY,1,0.3
MP,DENS,1,7.85e-09
! Elements
et,1,186
! Geometry
BLC4,0,0,1000,100,10
! Mesh
esize,5
vmesh,all
'''
>>> resp = mapdl.run_multiline(cmd)
>>> resp
You have already entered the general preprocessor (PREP7).
MATERIAL 1 EX = 200000.0
MATERIAL 1 NUXY = 0.3000000
MATERIAL 1 DENS = 0.7850000E-08
ELEMENT TYPE 1 IS SOLID186 3-D 20-NODE STRUCTURAL SOLID
KEYOPT( 1- 6)= 0 0 0 0 0 0
KEYOPT( 7-12)= 0 0 0 0 0 0
KEYOPT(13-18)= 0 0 0 0 0 0
CURRENT NODAL DOF SET IS UX UY UZ
THREE-DIMENSIONAL MODEL
CREATE A HEXAHEDRAL VOLUME WITH
X-DISTANCES FROM 0.000000000 TO 1000.000000
Y-DISTANCES FROM 0.000000000 TO 100.0000000
Z-DISTANCES FROM 0.000000000 TO 10.00000000
OUTPUT VOLUME = 1
DEFAULT ELEMENT DIVISIONS PER LINE BASED ON ELEMENT SIZE = 5.00
GENERATE NODES AND ELEMENTS IN ALL SELECTED VOLUMES
NUMBER OF VOLUMES MESHED = 1
MAXIMUM NODE NUMBER = 45765
MAXIMUM ELEMENT NUMBER = 8000
Alternatively, you can simply write the commands to a file and then
run it using Mapdl.input(). For
example, if you have a "ds.dat" generated from Ansys Mechanical,
you can run that with:
>>> resp = mapdl.input("ds.dat")
Conditional Statements and Loops¶
APDL conditional statements such as *IF must be either implemented
pythonically or using Mapdl.non_interactive. For example:
*IF,ARG1,EQ,0,THEN
*GET,ARG4,NX,ARG2 ! RETRIEVE COORDINATE LOCATIONS OF BOTH NODES
*GET,ARG5,NY,ARG2
*GET,ARG6,NZ,ARG2
*GET,ARG7,NX,ARG3
*GET,ARG8,NY,ARG3
*GET,ARG9,NZ,ARG3
*ELSE
*GET,ARG4,KX,ARG2 ! RETRIEVE COORDINATE LOCATIONS OF BOTH KEYPOINTS
*GET,ARG5,KY,ARG2
*GET,ARG6,KZ,ARG2
*GET,ARG7,KX,ARG3
*GET,ARG8,KY,ARG3
*GET,ARG9,KZ,ARG3
*ENDIF
Should be implemented as:
with mapdl.non_interactive:
mapdl.run("*IF,ARG1,EQ,0,THEN")
mapdl.run("*GET,ARG4,NX,ARG2 ") # RETRIEVE COORDINATE LOCATIONS OF BOTH NODES
mapdl.run("*GET,ARG5,NY,ARG2")
mapdl.run("*GET,ARG6,NZ,ARG2")
mapdl.run("*GET,ARG7,NX,ARG3")
mapdl.run("*GET,ARG8,NY,ARG3")
mapdl.run("*GET,ARG9,NZ,ARG3")
mapdl.run("*ELSE")
mapdl.run("*GET,ARG4,KX,ARG2 ") # RETRIEVE COORDINATE LOCATIONS OF BOTH KEYPOINTS
mapdl.run("*GET,ARG5,KY,ARG2")
mapdl.run("*GET,ARG6,KZ,ARG2")
mapdl.run("*GET,ARG7,KX,ARG3")
mapdl.run("*GET,ARG8,KY,ARG3")
mapdl.run("*GET,ARG9,KZ,ARG3")
mapdl.run("*ENDIF")
Or pythonically as:
# MAPDL parameters can be obtained using load_parameters
if ARG1 == 0:
mapdl.run("*GET,ARG4,NX,ARG2 ") # RETRIEVE COORDINATE LOCATIONS OF BOTH NODES
mapdl.run("*GET,ARG5,NY,ARG2")
mapdl.run("*GET,ARG6,NZ,ARG2")
mapdl.run("*GET,ARG7,NX,ARG3")
mapdl.run("*GET,ARG8,NY,ARG3")
mapdl.run("*GET,ARG9,NZ,ARG3")
else:
mapdl.run("*GET,ARG4,KX,ARG2 ") # RETRIEVE COORDINATE LOCATIONS OF BOTH KEYPOINTS
mapdl.run("*GET,ARG5,KY,ARG2")
mapdl.run("*GET,ARG6,KZ,ARG2")
mapdl.run("*GET,ARG7,KX,ARG3")
mapdl.run("*GET,ARG8,KY,ARG3")
mapdl.run("*GET,ARG9,KZ,ARG3")
APDL loops using *DO or *DOWHILE should also be implemetned
using mapdl.non_interactive or pythonically.
Warnings and Errors¶
Errors are handled pythonically. For example:
try:
mapdl.solve()
except:
# do something else with MAPDL
Commands that are ignored within MAPDL are flagged as errors. This is
different than MAPDL’s default behavior where commands that are
ignored are treated as warnings. For example, in ansys-mapdl-core
running a command in the wrong session raises an error:
>>> mapdl.finish()
>>> mapdl.k()
Exception:
K, , , ,
*** WARNING *** CP = 0.307 TIME= 11:05:01
K is not a recognized BEGIN command, abbreviation, or macro. This
command will be ignored.
You can change this behavior so ignored commands can be logged as
warnings not raised as an exception by setting
Mapdl.allow_ignore(). For
example:
>>> mapdl.allow_ignore = True
>>> mapdl.k() # warning silently ignored
Prompts¶
Prompts from MAPDL automatically continued as if MAPDL is in batch
mode. Commands requiring user input, such as Mapdl.vwrite() will fail and must be entered in
non-interactively.
APDL Command Logging¶
While ansys-mapdl-core is designed to make it easier to control an
APDL session by calling it using Python, it may be necessary to call
MAPDL again using an input file generated from a PyMAPDL script. This
is automatically enabled with the log_apdl='apdl.log' parameter.
Enabling this parameter will cause Mapdl to write each command run into a
log file named "apdl.log" in the active Mapdl.directory. For example:
from ansys.mapdl.core import launch_mapdl
ansys = launch_mapdl(log_apdl='apdl.log')
ansys.prep7()
ansys.k(1, 0, 0, 0)
ansys.k(2, 1, 0, 0)
ansys.k(3, 1, 1, 0)
ansys.k(4, 0, 1, 0)
Will write the following to "apdl.log"
/PREP7,
K,1,0,0,0
K,2,1,0,0
K,3,1,1,0
K,4,0,1,0
This allows for the translation of a Python script to an APDL script except for conditional statements, loops, or functions.
Interactive Breakpoint¶
In most circumstances it is necessary or preferable to open up the
MAPDL GUI. The Mapdl module has Mapdl.open_gui() that allows you to seamlessly open up the GUI without losing work or having to restart your session. For example:
>>> from ansys.mapdl.core import launch_mapdl
>>> mapdl = launch_mapdl()
Create a square area using keypoints
>>> mapdl.prep7()
>>> mapdl.k(1, 0, 0, 0)
>>> mapdl.k(2, 1, 0, 0)
>>> mapdl.k(3, 1, 1, 0)
>>> mapdl.k(4, 0, 1, 0)
>>> mapdl.l(1, 2)
>>> mapdl.l(2, 3)
>>> mapdl.l(3, 4)
>>> mapdl.l(4, 1)
>>> mapdl.al(1, 2, 3, 4)
Open up the gui
>>> mapdl.open_gui()
Resume where you left off
>>> mapdl.et(1, 'MESH200', 6)
>>> mapdl.amesh('all')
>>> mapdl.eplot()
This approach avoids the hassle of having to switch back and forth between an interactive session and a scripting session. Instead, you can have one scripting session and open up a GUI from the scripting session without losing work or progress. Additionally, none of the changes made in the GUI will affect the script. You can experiment in the GUI and the script will be left unaffected.
Running a Batch¶
Instead of running an MAPDL batch by calling MAPDL with an input file, you can instead define a function that runs MAPDL. This example runs a mesh convergence study based on the maximum stress of a cylinder with torsional loading.
import numpy as np
from ansys.mapdl.core import launch_mapdl
def cylinder_batch(elemsize, plot=False):
""" Report the maximum von Mises stress of a Cantilever supported cylinder"""
# clear
mapdl.finish()
mapdl.clear()
# cylinder parameters
radius = 2
h_tip = 2
height = 20
force = 100/radius
pressure = force/(h_tip*2*np.pi*radius)
mapdl.prep7()
mapdl.et(1, 186)
mapdl.et(2, 154)
mapdl.r(1)
mapdl.r(2)
# Aluminum properties (or something)
mapdl.mp('ex', 1, 10e6)
mapdl.mp('nuxy', 1, 0.3)
mapdl.mp('dens', 1, 0.1/386.1)
mapdl.mp('dens', 2, 0)
# Simple cylinder
for i in range(4):
mapdl.cylind(radius, '', '', height, 90*(i-1), 90*i)
mapdl.nummrg('kp')
# mesh cylinder
mapdl.lsel('s', 'loc', 'x', 0)
mapdl.lsel('r', 'loc', 'y', 0)
mapdl.lsel('r', 'loc', 'z', 0, height - h_tip)
# mapdl.lesize('all', elemsize*2)
mapdl.mshape(0)
mapdl.mshkey(1)
mapdl.esize(elemsize)
mapdl.allsel('all')
mapdl.vsweep('ALL')
mapdl.csys(1)
mapdl.asel('s', 'loc', 'z', '', height - h_tip + 0.0001)
mapdl.asel('r', 'loc', 'x', radius)
mapdl.local(11, 1)
mapdl.csys(0)
mapdl.aatt(2, 2, 2, 11)
mapdl.amesh('all')
mapdl.finish()
if plot:
mapdl.view(1, 1, 1, 1)
mapdl.eplot()
# new solution
mapdl.slashsolu()
mapdl.antype('static', 'new')
mapdl.eqslv('pcg', 1e-8)
# Apply tangential pressure
mapdl.esel('s', 'type', '', 2)
mapdl.sfe('all', 2, 'pres', '', pressure)
# Constrain bottom of cylinder/rod
mapdl.asel('s', 'loc', 'z', 0)
mapdl.nsla('s', 1)
mapdl.d('all', 'all')
mapdl.allsel()
mapdl.psf('pres', '', 2)
mapdl.pbc('u', 1)
mapdl.solve()
mapdl.finish()
# access results using MAPDL object
result = mapdl.result
# to access the results you could have run:
# from ansys.mapdl import reader as pymapdl_reader
# resultfile = os.path.join(mapdl.path, '%s.rst' % mapdl.jobname)
# result = pymapdl_reader.read_binary(result file)
# Get maximum von Mises stress at result 1
# Index 0 as it's zero based indexing
nodenum, stress = result.principal_nodal_stress(0)
# von Mises stress is the last column
# must be nanmax as the shell element stress is not recorded
maxstress = np.nanmax(stress[:, -1])
# return number of nodes and max stress
return nodenum.size, maxstress
# initialize MAPDL
mapdl = launch_mapdl(override=True, loglevel='ERROR')
# call MAPDL to solve repeatedly
result_summ = []
for elemsize in np.linspace(0.6, 0.15, 15):
# run the batch and report the results
nnode, maxstress = cylinder_batch(elemsize, plot=False)
result_summ.append([nnode, maxstress])
print('Element size %f: %6d nodes and maximum vom Mises stress %f'
% (elemsize, nnode, maxstress))
# Exit MAPDL
mapdl.exit()
This is the result from the script:
Element size 0.600000: 9657 nodes and maximum vom Mises stress 142.623505
Element size 0.567857: 10213 nodes and maximum vom Mises stress 142.697800
Element size 0.535714: 10769 nodes and maximum vom Mises stress 142.766510
Element size 0.503571: 14177 nodes and maximum vom Mises stress 142.585388
Element size 0.471429: 18371 nodes and maximum vom Mises stress 142.825684
Element size 0.439286: 19724 nodes and maximum vom Mises stress 142.841202
Element size 0.407143: 21412 nodes and maximum vom Mises stress 142.945984
Element size 0.375000: 33502 nodes and maximum vom Mises stress 142.913437
Element size 0.342857: 37877 nodes and maximum vom Mises stress 143.033401
Element size 0.310714: 59432 nodes and maximum vom Mises stress 143.328842
Element size 0.278571: 69106 nodes and maximum vom Mises stress 143.176086
Element size 0.246429: 110547 nodes and maximum vom Mises stress 143.499329
Element size 0.214286: 142496 nodes and maximum vom Mises stress 143.559128
Element size 0.182143: 211966 nodes and maximum vom Mises stress 143.953430
Element size 0.150000: 412324 nodes and maximum vom Mises stress 144.275406
Chaining Commands in MAPDL¶
MAPDL permits several commands on one line by using the separation
character "$". This can be utilized within ansys-mapdl-core
to effectively chain several commands together rather and send them to
MAPDL for execution rather than executing them individually. This can
be helpful when you need to execute thousands of commands in a python
loop and don’t need the individual results for each command. For
example, if you wish to create a 1000 keypoints along the X axis you
would run:
xloc = np.linspace(0, 1, 1000)
for x in xloc:
mapdl.k(x=x)
However, since each command executes individually and returns a
response, it is much faster to send the commands to be executed by
MAPDL in groups and have Mapdl handle grouping the commands by
using Mapdl.chain_commands.
xloc = np.linspace(0, 1, 1000)
with mapdl.chain_commands:
for x in xloc:
mapdl.k(x=x)
The execution time on this generally 4 to 10 times faster than running
each command individually. You can then view the final response of
the chained commands with Mapdl.last_response.
Note
Command chaining is not supported in distributed MAPDL. To improve
performances, use mute=True or Mapdl.non_interactive.
Sending Arrays to MAPDL¶
You can send numpy arrays or Python lists directly to MAPDL using
Mapdl.parameters <ansys.mapdl.core.parameters.Parameters.
This is far more efficient than individually sending parameters to
MAPDL through Python with Mapdl.run(). It uses Mapdl.vread() behind the scenes
and will be replaced with a faster interface in the future.
from ansys.mapdl.core import launch_mapdl
import numpy as np
mapdl = launch_mapdl()
arr = np.random.random((5, 3))
mapdl.parameters['MYARR'] = arr
Verify the data has been properly loaded to MAPDL by indexing
mapdl.parameters as if it was a Python dictionary:
>>> array_from_mapdl = mapdl.parameters['MYARR']
>>> array_from_mapdl
array([[0.65516567, 0.96977939, 0.3224993 ],
[0.58634927, 0.84392263, 0.18152529],
[0.76719759, 0.45748876, 0.56432361],
[0.78548338, 0.01042177, 0.57420062],
[0.33189362, 0.9681039 , 0.47525875]])
Downloading a Remote MAPDL File¶
When running MAPDL in gRPC mode, remote files can be listed and
downloaded using Mapdl
with Mapdl.download() For
example, to list the remote files and download one of them:
remote_files = mapdl.list_files()
# ensure the result file is one of the remote files
assert 'file.rst' in remote_files
# download the remote result file
mapdl.download('file.rst')
Note
This feature is only available for MAPDL 2021R1 or newer.
Uploading a Local MAPDL File¶
You can upload a local file a the remote mapdl instance with
Mapdl.upload() For example:
# upload a local file
mapdl.upload('sample.db')
# ensure the uploaded file is one of the remote files
remote_files = mapdl.list_files()
assert 'sample.db' in remote_files
Note
This feature is only available for MAPDL 2021R1 or newer.
Unsupported MAPDL Commands and Other Considerations¶
Most MAPDl commands have been mapped pythonically into their equivalent methods. Some commands, however, are not supported either because they are not applicable to an interactive session, or require additional commands that are incompatible with the way inputs are handled in the MAPDL server.
Non-Applicable Commands¶
Some commands are quietly ignored by MAPDL and you are still free to
use them. For example /BATCH, implemented as Mapdl.batch() returns:
*** WARNING *** CP = 0.519 TIME= 12:04:16
The /BATCH command must be the first line of input. The /BATCH command
is ignored.
Note, that running these commands with mapdl.run('<command>') will
not cause MAPDL to exit, and will generally simply be ignored by MAPDL.
Ignored commands:
/BATCH*DEL/ERASEERASEHELPHELPDISPNOERASEUNDO*VEDIT
Unsupported “Interactive” Commands¶
The following commands will immediately kill the server if run and are not permitted.
Some commands, such as /EOF, . These commands are not wrapped or
directly exposed to the user with a Python method such as
mapdl.eof(). If you wish to exit the server, use
Mapdl.exit(). Other commands,
such as *ASK, request user and are not supported within an
interactive context. Some of commands may be run in
Mapdl.non_interactive. Others simply are not
supported.
*ASK*CREATECFOPEN*CYCLE*DO*DOWHILE*ELSE*ELSEIF*ENDDO/EOF*GO*IF*REPEAT*RETURN*VWRITECMATRIX
Note, many of these commands do not make sense in a Python context.
For example the *ASK can be replaced with a Python input,
*IF with a Python if statement, and instead of *CREATE and
*USE can simply call another Python function or module.
The command CMATRIX does not kill the server, however when it is
run on interactive mode does not make any effect. This command needs to
be run in non_interactive mode (Mapdl.non_interactive).
GUI Commands¶
These commands have no direct mapping to MAPDL as they are not applicable to a “headless” interactive session.
*DEL
Environment Variables¶
There are several PyMAPDL specific environment variables that can be used to control the behavior or launching of PyMAPDL and MAPDL. These include:
ANSYSLMD_LICENSE_FILE |
License file or IP address (e.g. 192.168.0.16). This is helpful for supplying licencing for docker. |
PYMAPDL_MAX_MESSAGE_LENGTH |
Maximum gRPC message length. If your connection terminates when running PRNSOL or NLIST, raise this. In bytes, defaults to 256 MB |
PYMAPDL_PORT |
Default port to look for when connecting PyMAPDL. Normally used for unit testing. |
PYMAPDL_START_INSTANCE |
Override the behavior of
|