Write to specific row in CSV according to query Python

There is no way to insert data in the middle of a file. Writing to the middle of a file will overwrite the data at that position. Instead:

• open the file in read mode
• read all the data in the file
• close the file
• reopen the file in write mode
• write the first few lines
• write your extra data
• write the rest of the original data

an example:

with open('test.csv') as f:
l = f.readlines()

l[4] += '0'
with open('test2.csv', 'w') as f:
    f.writelines(l)

with open('text.csv', 'r') as f:
    rows = [x.split() for x in f]
with open('text_1.csv', 'w') as f:
    for row in rows:
        f.write(row[0] + " " + row[1])
        if row[0] == '111': # or you can check for multiple values here.
            f.write("0")
        f.write("\n")

This will let you open, read and write to the file within a single context manager in one shot.

search_term = '112' # This is what you are looking 
                    # for at the start of the lines.
##-------------------------------------------------------##
# Define separator
sep = '\t' # Use '\t' (TAB) or " " (SPACE)
val = 0 # This is the value you want to insert 
        # at the end of the target line.
##-------------------------------------------------------##
write_to_file = False # Set this to True when 
                      # you want to write to the file.

##-------------------------------------------------------##
with open("dummy.csv","r+") as f:
    content = f.readlines()
    for i,line in enumerate(content):
        if line.startswith(search_term):
            line = line.strip() + '{}{}\n'.format(sep,val)
            content[i] = line
    if write_to_file:
        f.writelines(content)

print(''.join(content))