从文本转换为CSV后为空文件

Question

I have been writing a short piece of python code to download a data file from a website and write it to a text file (which it does successfully). Now I want to take that text file and convert it to CSV format. I have been using the responses from questions like "How to convert from txt to csv" but still come to the same end, which is that the CSV file is created successfully and the code executes without error, only the CSV file is empty, short of the column titles I have defined.

import csv
import requests
res = requests.get('https://www.physics.rutgers.edu/~saurabh/mlcs2k2/vectors_R.dat')
res.status_code = requests.codes.ok


textfile = open("textfile.txt","w")
textfile.write(res.text)


with open('textfile.txt', 'r') as in_file:
    stripped = (line.strip() for line in in_file)
    lines = (line.split(",") for line in stripped if line)
    with open('csvfile.csv', 'w') as out_file:
        writer = csv.writer(out_file)
        writer.writerow(('Phase', 'M^0_R', 'P_R', 'Q_R')) #Prints correctly                                                                                                            
        writer.writerows(lines)

Answer 1

When you write data to textfile, you leave the file open. Therefore when you reopen it later, the cursor is already in the end of the file, and iterating over lines only continues forward from the cursor, not from the beginning of the file.

Fix this by closing file after opening:

textfile = open("textfile.txt","w")
textfile.write(res.text)
textfile.close()