Python replace string in loop for a text file

Question

I have been trying to modify a specific word in a text file, using a for loop. The word I wish to change in the Fe.in file is >latt_par. I would like to create one file for each value of vol in the list. However, I just keep getting the last one "3.05". Is there a way you can guide me please? I am starting in Python.

Here is my code

vols = [2.65, 2.85, 3.05] 
temp = [100,200,300]
for x in vols:
  f = open('Fe.in','r')
  filedata = f.read()
  f.close()
  newvol = filedata.replace("latt_par", str(x))
f = open('Fe_' + str(x) +'.in','w')
f.write(newvol)
f.close()

I would also like to replace another string in the file Fe.in, which I want to run over the variable temp, but I have not been able to. Any help is greatly appreciated!

Your write to file is outside of your loop, meaning it runs once, after the final iteration. This would yield a filename of `3.05` as it is your last iteration. — PacketLoss, Jan 12 '21 at 04:38

Synthase · Accepted Answer · 2021-01-12T05:50:25.280

0

with open('Fe.in','r') as msg:
    data = msg.read()

for x in vols:
    wdata = data.replace("latt_par", str(x))

    with open('Fe_' + str(x) +'.in','w') as out_msg:
        out_msg.write(wdata)

Like that you don't need to open your template N times, and the with method allows to not close the file with no troubles.

edited Jan 12 '21 at 05:50

answered Jan 12 '21 at 04:42

Synthase

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Hello @Synthase. Thanks for your time. I tried with this one but got error `ValueError: I/O operation on closed file. ` . It only creates the file with the first value in vols, but an empty file – Valeria Itzel Arteaga Muñiz Jan 12 '21 at 05:39
Sorry. I edited my answer – Synthase Jan 12 '21 at 05:50
Thank you a lot! It worked this time. I have another quick question if you dont mind. I would like to make another replacement for another variable.Can I just add another wdata2 variable? How can I print that in the same file? – Valeria Itzel Arteaga Muñiz Jan 12 '21 at 06:03
If you want two changes in the same wdata message, just do: wdata = data.replace("latt_par", str(x)).replace("tmp", str(y)). If that was helpful, think about accepting the answer ;) (gray tick top left of my answer) – Synthase Jan 12 '21 at 06:05
Oh, okay, I will try that. Thank you, your response was very helpful! – Valeria Itzel Arteaga Muñiz Jan 12 '21 at 06:07

Python replace string in loop for a text file

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