用list替换Python中的第一行

Question

I would like to replace the first row of my csv file. The csv file is generated by a script that opens other csv files and reads some columns. It looks like

TimeStamp;Value;Value; ...
2014/08/04 21:00:53.575;0.168889;1.146; ...
2014/08/04 21:01:23.590;0.168889;1.138; ...
2014/08/04 21:01:53.595;0.17;1.154; ...
2014/08/04 21:02:23.585;0.168889;1.205; ...

I would like to replace the first row (Timestamp;Value;Value) with the names is saved in a list.

The output I want should be

TimeStampfromlist;Firstnamefromlist;Secondnamefromlist; ...
2014/08/04 21:00:53.575;0.168889;1.146; ...
2014/08/04 21:01:23.590;0.168889;1.138; ...
2014/08/04 21:01:53.595;0.17;1.154; ...
2014/08/04 21:02:23.585;0.168889;1.205; ...

How can I do that?

---

Trying to be more specific this is the code I use to generate my csv file

import csv
import glob
import os, sys

path = "C:/Users/ButoeruG/Desktop/pythonscripts/prova"
dirs = glob.glob('*.csv')
namelist = dirs

print dirs[0]

file1 = dirs[1]
print file1
for file in namelist:
    namelist = file.partition("TrendLogExtended_")[2].partition("-Ext).csv")[0]
    print namelist


primofile = csv.reader(open(file1, 'rb'), delimiter=";", quotechar='|')
output_rows = []

for row in primofile:
    output_rows.append([row[2], row[15]])

for file in dirs:
    data = csv.reader(open(file, 'rb'), delimiter=";", quotechar='|')
    column = []
    for idx,row in enumerate(data):
        output_rows[idx].append(row[15])

with open("provaoutput.csv", 'wb') as f:
    writer = csv.writer(f, delimiter=';')
    for row in output_rows:
        writer.writerow(row)

Now the point is that when I write the row[15] I just copy from a file a column that looks like:

Value;
1,956;
1;054;
1,456;

I would like to replace value with part of the file name that I saved in namelist.

Answer 1

You can use the the csv module but this logic will do what you need.

l = ["TimeStampfromlist","Firstnamefromlist","Secondnamefromlist"]

with open("in.csv", 'r') as data_file:
    lines = data_file.readlines()
    lines[0]= ":".join(l)+"\n" # replace first line, the "header" with list contents
    with open("in.csv", 'w') as out_data:
        for line in lines: # write updated lines
            out_data.write(line)

Answer 2

The general approach is open file for reading, skip the old header line, open target file for writing, write the new header line, then copy over the rest of the file. At the end rename new file to old file.

import os

new_headers = ['TimeStampfromlist', 'Firstnamefromlist', 'Secondnamefromlist']
filename = 'data.csv'
with open(filename, 'r') as lines:
    next(lines)  # Skip first line.
    tmp_filename = filename + '.tmp'
    with open(tmp_filename, 'w') as out_file:
        out_file.write(':'.join(new_headers) + '\n')
        out_file.writelines(lines)
    os.rename(tmp_filename, filename)