在python中操作csv文件并将其输出写入新的csv文件

Question

我有一个简单的文件名为萨利姆.csv其中包含以下csv信息行：

File,Run,Module,Name,,,,,  
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithInterference,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithoutInterference,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithInterferencePartial,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithoutInterferencePartial,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithInterferenceDropped,0,NaN,NaN,NaN,NaN  
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].nic.phy,nbFramesWithoutInterferenceDropped,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].appl,broadcast queued,3,NaN,NaN,NaN,NaN  
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].appl,replies sent,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].appl,replies received,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,nominal,1.188e+07,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,total,1232.22,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,lifetime,-1,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,Mean power consumption,55.7565,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,num devices,1,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,physical layer,0,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,device total (mWs),1232.22,NaN,NaN,NaN,NaN
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,account,0,1,2,3,4
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,energy (mWs),0,207.519,1024.7,0,0
General-0.sca,General-0-20160706-14:58:51-10463,MyNetwork.node[0].batteryStats,time (s),0,3.83442,18.2656,0,

我想跳过第一行，读取此文件，只将列[2]和列[4]写入名为输出.csv. 我已经写了以下脚本来做这项工作。你知道吗

import csv

with open('saleem.csv') as f:
    readcsv = csv.reader(f)

    for row in readcsv:
            dele = (row[2], row[4])
            print dele
with open('out.csv', 'w+') as j:
    writecsv = csv.writer(j)
    #for row in dele:
    for row in dele:
            writecsv.writerows(dele)

f.close()
j.close()

这将产生以下输出：

M,y,N,e,t,w,o,r,k,.,n,o,d,e,[,4,],.,b,a,t,t,e,r,y,S,t,a,t,s
0
M,y,N,e,t,w,o,r,k,.,n,o,d,e,[,4,],.,b,a,t,t,e,r,y,S,t,a,t,s
0

请帮帮我，对不起之前的错误请，因为我写错了行。你知道吗

Answer 1

编辑以反映修改后的问题

我看到一些问题：

P1:writerows(...)

for row in dele:
            writecsv.writerows(dele)

writerows获取要写入csv文件的行列表。因此，它不应该在循环中遍历所有行并尝试单独编写它们。你知道吗

P2:覆盖

for row in readcsv:
            dele = (row[2], row[4])

您正在不断地覆盖dele，因此您不会从每一行跟踪row[2]和row[4]。你知道吗

你可以做些什么：

dele = []
with open('saleem.csv') as f:
    readcsv = csv.reader(f)
    for row in readcsv:
        dele.append([row[2], row[4])
        print([row[2], row[4]])

with open('out.csv', 'w+') as j:
    writecsv.csvwriter(j)
    writecsv.writerows(dele)

这产生了输出：

MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].nic.phy,0
MyNetwork.node[0].appl,3
MyNetwork.node[0].appl,0
MyNetwork.node[0].appl,0
MyNetwork.node[0].batteryStats,1.188e+07
MyNetwork.node[0].batteryStats,1232.22
MyNetwork.node[0].batteryStats,-1
MyNetwork.node[0].batteryStats,55.7565
MyNetwork.node[0].batteryStats,1
MyNetwork.node[0].batteryStats,0
MyNetwork.node[0].batteryStats,1232.22
MyNetwork.node[0].batteryStats,0
MyNetwork.node[0].batteryStats,0
MyNetwork.node[0].batteryStats,0

此外，与您手头的问题无关，不需要以下代码：

f.close()
j.close()

with open(...):语法之所以被广泛使用，是因为它能为您优雅地关闭文件。你不需要自己单独关闭它。一旦with块结束，文件就会关闭。你知道吗

Answer 2

我建议使用pandas库。你知道吗

这使得使用csv文件非常容易。你知道吗

import pandas as pd #standard convention for importing pandas

# reads the csv file into a pandas dataframe
dataframe = pd.read_csv('saleem.csv') 

# make a new dataframe with just columns 2 and 4 
print_dataframe = dataframe.iloc[:,[2,4]] 

# output the csv file, but don't include the index numbers or header, just the data
print_dataframe.to_csv('out.csv', index=False, header=False) 

如果你使用Ipython或Jupyter笔记本，你可以打字

dataframe.head()

查看数据帧的前几个值。您可以使用该库做更多值得学习的事情，但一般来说，它是读取、过滤和处理csv数据的好方法。你知道吗