具有多个Python命令的R系统调用

Question

I need to pass multiple python commands into one system call (in R), and I am having difficulty with the syntax.

What I'm trying to combine:

system("python "file1.py" -f "module_to_load1.py" -o "output_loc_file1"")
system("python "file2.py" -f "module_to_load2.py" -o "output_loc_file2"")

Simplified code:

 pystr="python -c print('hi')"
 system(paste(pystr, " && ", pystr, sep=""))

My desired output is:

hi
hi

If I enter the code directly into the command prompt, I get the desired output:

python -c print('hi') && python -c print('hi')

>> hi
>> hi

However, the system call is only returning a single 'hi', and I can't figure out what my dumb error is. Any help would be much appreciated.

Answer 1

You're better off storing it as a script than trying to manage a messy system call:

file: my.py

print "hi"
print "hi"

Then from R:

> system("python my.py")
hi
hi

In the case that your actual code is much more complicated, you can generate python code and write it to a file that you then call.

Answer 2

You can't just line up quotes like that -- embedded quotes need to be escaped. So instead of

system("python "file1.py" -f "module_to_load1.py" -o "output_loc_file1"")

do

system("python \"file1.py\" -f \"module_to_load1.py\" -o \"output_loc_file1\"")

or simply omit the quotes as the filenames do not contain troublesome characters:

system("python file1.py -f module_to_load1.py -o output_loc_file1")

The recommendation about writing proper Python scripts is still a good one.