Use subprocess in python to echo a variable

Question

I have a variable in python, and I'm trying to open a subprocess and echo the variable, then create a file with the variable in it. I tried this:

subprocess.Popen(['echo "$var" > file.txt'], shell=True)

It creates the file, but it's empty. How can I get the result that I want?

Not sure of your use case, but it might be easier and more robust to open the file, format the variable appropriately into a string, and write the string to the file. — Mark Plotnick, Oct 18 '18 at 18:12

score 2 · Accepted Answer · answered Oct 18 '18 at 18:12

In Python you don't use $ sign to use a variable. Also when you want to embed variable into string, you cannot just simply use variable name in string. You should do something like that:

subprocess.Popen(['echo "{}" > file.txt'.format(var)], shell=True)

This is great website which will explain you how to use .format method.

Use subprocess in python to echo a variable

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