Awk, bash or python for converting a regular file?

Question

Hi, I have a text file with lots of lines and with this structure:

[('name_1a',
'name_1b',
value_1),
('name_2a',
'name_2b',
value_2),
.....
.....
('name_XXXa',
'name_XXXb',
value_XXX)]

I would like to convert it to:

name_1a, name_1b, value_1
name_2a, name_2b, value_2
......
name_XXXa, name_XXXb, value_XXX

I wonder what would be the best way, whether awk, python or bash.

Thanks

Jose

Answer 1

It looks like legal Python. You might be able to just import it as a module and then write it back out after formatting it.

Answer 2

Awk is typically line oriented, and bash is a shell, with limited numbrer of string manipulation functions. It really depends on where your strength as a programmer lies, but all other things being equal, I would choose python.

Did you ever consider that by redirecting the time it took to post this on SO, you could have had it done?

"AWK is a language for processing files of text. A file is treated as a sequence of records, and by default each line is a record. Each line is broken up into a sequence of fields, so we can think of the first word in a line as the first field, the second word as the second field, and so on. An AWK program is of a sequence of pattern-action statements. AWK reads the input a line at a time. A line is scanned for each pattern in the program, and for each pattern that matches, the associated action is executed." - Alfred V. Aho[2]

Answer 3

Tried evaluating it python? Looks like a list of tuples to me.

eval(your_string)

Note, it's massively unsafe! If there's code in there to delete your hard disk, evaluating it will run that code!

Answer 4

Asking what's the best language for doing a given task is a very different question to say, asking: 'what's the best way of doing a given task in a particular language'. The first, what you're asking, is in most cases entirely subjective.

Since this is a fairly simple task, I would suggest going with what you know (unless you're doing this for learning purposes, which I doubt).
If you know any of the languages you suggested, go ahead and solve this in a matter of minutes. If you know none of them, now enters the subjective part, I would suggest learning Python, since it's so much more fun than the other 2 ;)

Answer 5

I would like to use Python:

lines = open('filename.txt','r').readlines()
n = len(lines) # n % 3 == 0
for i in range(0,n,3):
    name1 = lines[i].strip("',[]\n\r")
    name2 = lines[i+1].strip("',[]\n\r")
    value = lines[i+2].strip("',[]\n\r")
    print name1,name2,value

Answer 6

If the values are legal python values, you can take advantage of eval() since your data is a legal python data sucture. The following would work if values are integers, otherwise you might have to massage the print call a bit:

input = """[('name_1a',
          'name_1b',
          1),
         ('name_2a',
          'name_2b',
          2),
         ('name_XXXa',
          'name_XXXb',
          3)]"""

for e in eval(input):
    print '%s,%s,%d' % e

P.S. using eval() is quite controversial since it will execute any valid python code that you pass into it, so take care.

Answer 7

Oh boy, here is a job for ast.literal_eval: (literal_eval is safer than eval, since it restricts the input string to literals such as strings, numbers, tuples, lists, dicts, booleans and None:

import ast
filename='in'
with open(filename,'r') as f:
    contents=f.read()
    data=ast.literal_eval(contents)

for elt in data:
    print(', '.join(map(str,elt)))

Answer 8

here's one way to do it with (g)awk

$ awk -vRS=")," ' { gsub(/\n|[\047\]\[)(]/,"") } 1' file
name_1a,name_1b,value_1
name_2a,name_2b,value_2
name_XXXa,name_XXXb,value_XXX