How do I parse a file and substitute the environment variables with values in Python

Question

I have a text file (lets call it file1.txt), it contains the following lines: "read model $path_1"

How do I replace the value of path_1 variable in this text file and write it to another file (lets call it file2.txt) with same contents but $path_1 variable expanded. My file2.txt should contain something like the following: "read model /home/Aero/test"

Is there any parser in python available to do this job? I looked into ConfigParser module but looks to me that it needs a config file with variable=value pair.

Regards, Sandhya

Ignacio Vazquez-Abrams · Accepted Answer · 2011-03-28 05:24:28Z

4

os.path.expandvars()

answered Mar 28, 2011 at 5:24

Ignacio Vazquez-Abrams

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2 Comments

Sandhya Jha Over a year ago

This works. Thank you. But is there a way to make it work for even shell variables, say I set some variable $path_1=/home/Aero/test in the shell, but using os.path.expandvars("path_1") doesn't work.

invert Over a year ago

Maybe because you are setting shell (bash) variables, and not environment variables, @Sandhya. Try using EXPORT or SET nixcraft.com/shell-scripting/…

linbo · Accepted Answer · 2011-03-28 05:39:20Z

3

string.Template

>>> from string import Template
>>> s = Template('$who likes $what')
>>> s.substitute(who='tim', what='kung pao')
'tim likes kung pao'

answered Mar 28, 2011 at 5:39

linbo

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