how to write the output to a file python

Question

so I have the file: data2.txt

Lollypop,
Lolly pop,
ooh 
lolly,
lolly, lolly;
lollypop, lollypop,
ooh lolly, lolly, lolly,
lollypop!
ba dum dum dum ...

LOL :-)

i need to loop through each line of data2.txt printing only lines that contain the string 'lol' and print the output to a newfile

with open("data3.txt") as g:
    with open("data2.txt") as lfp:
        for lin in lfp:
            if 'lol' in lin:
                g.write(str(lin))
            elif 'LOL' in lin:
                g.write(str(lin))
            elif 'Lol' in lin:
                g.write(str(lin))

But I keep getting error:

    g.write(str(lin))
io.UnsupportedOperation: not writable

Padraic Cunningham · Accepted Answer · 2015-12-12 13:36:01Z

5

You need to open with w for writing:

with open("data3.txt","w") as g:
    with open("data2.txt") as lfp:

You can also simplify to:

with open("data3.txt", "w") as g, open("data2.txt") as lfp:
        for lin in lfp:
            if 'lol' in lin.lower():
                g.write(lin)

Or use writelines:

with open("data3.txt", "w") as g, open("data2.txt") as lfp:
        g.writelines(line for line in lfp if "lol" in line.lower())

line is already a string so you don't need to call str on it, using "lol" in line.lower() will match all you cases.

If you were explicitly looking for "lol", "Lol", "LOL", any would be a nicer approach.

with open("data3.txt", "w") as g, open("data2.txt") as lfp:
    poss = ("lol", "Lol", "LOL")
    g.writelines(line for line in lfp 
                    if any(s in line for s in poss))

All the modes are explained in the docs

edited Dec 12, 2015 at 13:36

answered Dec 12, 2015 at 13:29

Padraic Cunningham

181k30 gold badges264 silver badges327 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

martijnn2008 Over a year ago

didn't know you can open two files on one line, nice answer!

Padraic Cunningham Over a year ago

@martijnn2008, yep, you can open as many as you want, you can so it with any objects the support the use of a context manager

DeepSpace · Accepted Answer · 2015-12-12 13:30:18Z

0

The problem is in the line with open("data3.txt") as g:

You didn't provide open with a mode, and the default is r which is only for reading. Use with open("data3.txt", 'w') as g: if you want to replace the file if it is already exists or with open("data3.txt", 'a') as g: if you want to append to the file if it is already exists.

edited Dec 12, 2015 at 13:30

answered Dec 12, 2015 at 13:29

DeepSpace

82.1k12 gold badges119 silver badges166 bronze badges

Collectives™ on Stack Overflow

how to write the output to a file python

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related