Question

save = "/root/foo/"
PERF_PATH="/root/foobar/"

So, Initially I had the variable save and perf_path in the cmd. but now, I want to substitute it for enhanced readability.

I wanted to create a folder into which the variable app[a] will eventually get stored.

direc = os.mkdir(save + i + "-"+ j +"-" + k + "-" +l)

Creating a directory does not seem to a problem.
but joining a non-string value variable to a string seems to be a problem.

cmd = "taskset -c %s" + PERF_PATH + "perf2 stat -t %s e r4008387e1 -f -o" +save + direc + "%s.csv &" % (cpus_list[a],fpid[a],apps[a])
pro= subprocess.Popen(cmd,shell=True, stdout=subprocess.PIPE, preexec_fn=os.setsid)

TypeError: cannot concatenate 'str' and 'NoneType' objects

cmd = "taskset -c %s" + str(PERF_PATH) + "perf2 stat -t %s e r4008387e1 -f -o" +str(save) + str(direc) + "%s.csv &" % (cpus_list[a],fpid[a],apps[a])

that wasn’t of much help either.

any ideas how I can solve this?

Answer 1

os.mkdir() does not return anything, so direc is set to None.

Do this instead:

direc = save + i + "-"+ j +"-" + k + "-" +l
os.mkdir(direc)

You really want to use os.path.join() and string formatting to build paths though, it’ll be a lot easier to read:

save = "/root/foo"
PERF_PATH="/root/foobar"

direc = os.path.join(save, '-'.join((i, j, k, l)))
os.mkdir(direc)

For subprocess.Popen(), pass in a list instead of a string for the command and arguments, and leave shell to the default value of False, there is no need to have the shell handle that:

cmd = ['taskset', 
    '-c', cpus_list[a], PERF_PATH, 'perf2', 'stat',
    '-t', fpid[a], 'e', 'r4008387e1',
    '-f', '-o', save, 
    os.path.join(direc, "%s.csv" % apps[a])
]

pro = subprocess.Popen(cmd, stdout=subprocess.PIPE, preexec_fn=os.setsid)