在 Python3 中执行链式 bash 命令，包括多个管道和 grep

Question

I have to use the below bash command in a python script which includes multiple pip and grep commands.

 grep name | cut -d':' -f2  | tr -d '"'| tr -d ','

I tried to do the same using subprocess module but didn't succeed.

Can anyone help me to run the above command in Python3 scripts?

I have to get the below output from a file file.txt .

 Tom
 Jack

file.txt contains:

"name": "Tom",
"Age": 10

"name": "Jack",
"Age": 15

Actually I want to know how can run the below bash command using Python.

    cat file.txt | grep name | cut -d':' -f2 | tr -d '"'| tr -d ','

Answer 1

This works without having to use the subprocess library or any other os cmd related library, only Python.

my_file = open("./file.txt")
line = True
while line:
    line = my_file.readline()
    line_array = line.split()
    try:
        if line_array[0] == '"name":':
            print(line_array[1].replace('"', '').replace(',', ''))
    except IndexError:
        pass
my_file.close()

Answer 2

If you not trying to parse a json file or any other structured file for which using a parser would be the best approach, just change your command into:

grep -oP '(?<="name":[[:blank:]]").*(?=",)' file.txt

You do not need any pipe at all.

This will give you the output :

Tom
Jack

Explanations:

• -P activate perl regex for lookahead/lookbehind
• -o just output the matching string not the whole line
• Regex used: (?<="name":[[:blank:]]").*(?=",)
  • (?<="name":[[:blank:]]") Positive lookbehind: to force the constraint "name": followed by a blank char and then another double quote " the name followed by a double quote " extracted via (?=",) positive lookahead

demo : https://regex101.com/r/JvLCkO/1