Question

I would like to find a better solution to achieve the following three steps:

1. read strings at a given row
2. update strings
3. write the updated strings back

Below are my code which works but I am wondering is there any better (simple) solutions?

new='99999'

f=open('C:/Users/th/Dropbox/com/MS1Ctt-P-temp.INP','r+')
lines=f.readlines()
#the row number we want to update is given, so just load the content
x = lines[95]
print(x)
f.close()


#replace
f1=open('C:/Users/th/Dropbox/com/MS1Ctt-P-temp.INP')
con = f1.read()
print con
con1 = con.replace(x[2:8],new) #only certain columns in this row needs to be updated
print con1
f1.close()


#write
f2 = open('C:/Users/th/Dropbox/com/MS1Ctt-P-temp.INP', 'w')
f2.write(con1)
f2.close()

Thanks!
UPDATE: get an idea from jtmoulia this time it becomes easier

def replace_line(file_name, line_num, col_s, col_e, text):
    lines = open(file_name, 'r').readlines()
    temp=lines[line_num]
    temp = temp.replace(temp[col_s:col_e],text)
    lines[line_num]=temp
    out = open(file_name, 'w')
    out.writelines(lines)
    out.close()

Answer 1

Well, to begin with you don’t need to keep reopening and reading from the file every time. The r+ mode allows you to read and write to the given file.

Perhaps something like

with open('C:/Users/th/Dropbox/com/MS1Ctt-P-temp.INP', 'r+') as f:
    lines = f.readlines()
    #... Perform whatever replacement you'd like on lines
    f.seek(0)
    f.writelines(lines)

Also, Editing specific line in text file in python