如何從csv文件中提取和複製行到python中的另一個csv文件？

Question

讓我們假設我有一個CSV文件中的大數據：這是一組從我的文件中的行：

frame.number frame.len frame.cap_len frame.Type 
    1    100   100   ICMP_tt 
    2    64   64   UDP 
    3    100   100   ICMP_tt 
    4    87   64   ICMP_nn 

我想從這個文件中提取30％，並把它放在另一個csv文件。

我嘗試通過使用此代碼，但它給了我選擇每行，每行不：

import csv 

data = [] #Buffer list 
with open("E:\\Test.csv", "rb") as the_file: 
    reader = csv.reader(the_file, delimiter=",") 
    for line in reader: 

     try: 
      new_line = [line[0], line[1]] 
      #Basically ´write the rows to a list 
      data.append(new_line) 
     except IndexError as e: 
      print e 
      pass 

    with open("E:\\NewTest.csv", "w+") as to_file: 
     writer = csv.writer(to_file, delimiter=",") 
     for new_line in data: 
      writer.writerow(new_line) 

我嘗試

Answer 1

的Python csv模塊使用,默認情況下，所以它不需要指定分隔符，除非你有一個不同的分隔符。我想你有以下csv文件：

frame.number,frame.len,frame.cap_len,frame.Type 
1,100,100,ICMP_tt 
2,64,64,UDP 
3,100,100,ICMP_tt 
4,87,64,ICMP_nn 

該文件中的每一行代表一行。

# read 
data = [] 
with open('test.csv', 'r') as f: 
    f_csv = csv.reader(f) 
    # header = next(f_csv) 
    for row in f_csv: 
     data.append(row) 


# write 
with open('newtest.csv', 'w+') as f: 
    writer = csv.writer(f) 
    for i in range(int(len(data) * 30/100)): 
     writer.writerow(data[i])