You need to have better understanding of the python language and its standard library to translate the expression
cat "$filename": Reads the file cat "$filename" and dumps the content to stdout
|: pipe redirects the stdout from previous command and feeds it to the stdin of the next command
grep "something": Searches the regular expressionsomething plain text data file (if specified) or in the stdin and returns the matching lines.
cut -d'"' -f2: Splits the string with the specific delimiter and indexes/splices particular fields from the resultant list
Python Equivalent
cat "$filename" | with open("$filename",'r') as fin: | Read the file Sequentially
| for line in fin: |
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grep 'something' | import re | The python version returns
| line = re.findall(r'something', line)[0] | a list of matches. We are only
| | interested in the zero group
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cut -d'"' -f2 | line = line.split('"')[1] | Splits the string and selects
| | the second field (which is
| | index 1 in python)
import re
with open("filename") as origin_file:
for line in origin_file:
line = re.findall(r'something', line)
if line:
line = line[0].split('"')[1]
print line