How to Use with with OpenSeesPy

Original Post - 17 Jan 2024 - Michael H. Scott

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The with command offers a clean approach to manage Python resources, particularly file streams. Without going into detail, the with command is a shortcut for exception handling.

The nice thing about reading and writing files using the with command is you don’t have to worry about closing the file stream. Immediately after the with block goes out of scope, the stream is closed automatically.

So, instead of doing this:

output = open('concrete23.txt','w')
output.write('I love Concrete23!\n')
output.close()

and potentially forgetting to call close(), you can do this:

with open('concrete23.txt','w') as output:
    output.write('I love Concrete23!\n')

and the file stream will be closed for you.

It has taken me a while to get familiar with the with command, but here are a few use cases that make sense with OpenSees.

First is writing bespoke analysis results files.

#
# Define your model and analysis
#

with open('myResults.csv','w') as output:
    for i in range(Nsteps):
        ops.analyze(1,dt)
        output.write(f'{ops.getTime()},{ops.nodeDisp(2,1)}\n')

Along the same lines, the second use is calling the OpenSees Tcl to Python converter.

exec(open('toOpenSeesPy.py').read())

with open('beam.py','w') as outfile:
    outfile.write('import openseespy.opensees as ops\n\n')
    toOpenSeesPy('beam.tcl',outfile,'ops')

Yeah, I know, I should stop using exec-open-read, a convoluted equivalent to Tcl’s source command, and learn how to better use the import command.

The third use is reading the maximum absolute response from the file generated by an envelope recorder, whose first line is max, second line is min, and third line (index 2) is max abs.

#
# Define your model and analysis
#

ops.recorder('EnvelopeNode','-file','node.out','-node',2,'-dof',1,'disp')

ops.analyze(Nsteps,dt)

umax = 0
with open('node.out','r') as result:
    contents = result.readlines()
    umax = contents[2]

If you have come across other crafty uses of the with command in OpenSees, please share in the Comments section below.

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