python讀取CSV文件

python中有一個讀寫csv文件的包,直接import csv便可。利用這個python包能夠很方便對csv文件進行操做,一些簡單的用法以下。html

1. 讀文件python

csv_reader = csv.reader(open('data.file', encoding='utf-8'))
    for row in csv_reader:
        print(row)

例若有以下的文件函數

輸出結果以下post

['0.093700','0.139771','0.062774','0.007698']ui

['-0.022711','-0.050504','-0.035691','-0.065434']this

['-0.090407','0.021198','0.208712','0.102752']spa

['-0.085235','0.009540','-0.013228','0.094063'].net

可見csv_reader把每一行數據轉化成了一個list,list中每一個元素是一個字符串excel

2. 寫文件code

讀文件時,咱們把csv文件讀入列表中,寫文件時會把列表中的元素寫入到csv文件中。

list = ['1', '2','3','4']
out = open(outfile, 'w') csv_writer = csv.writer(out) csv_writer.writerow(list)

可能遇到的問題:直接使用這種寫法會致使文件每一行後面會多一個空行。

解決辦法以下:

out = open(outfile, 'w', newline='')
csv_writer = csv.writer(out, dialect='excel')
csv_writer.writerow(list)

參考以下:

在stackoverflow上找到了比較經典的解釋,原來 python3裏面對 str和bytes類型作了嚴格的區分,不像python2裏面某些函數裏能夠混用。因此用python3來寫wirterow時,打開文件不要用wb模式,只須要使用w模式,而後帶上newline=''。 

In Python 2.X, it was required to open the csvfile with 'b' because the csv module does its own line termination handling.

In Python 3.X, the csv module still does its own line termination handling, but still needs to know an encoding for Unicode strings. The correct way to open a csv file for writing is:

outputfile=open("out.csv",'w',encoding='utf8',newline='')

encoding can be whatever you require, but newline='' suppresses text mode newline handling. On Windows, failing to do this will write \r\r\n file line endings instead of the correct \r\n. This is mentioned in the 3.X csv.reader documentation only, but csv.writer requires it as well.

連接:http://blog.csdn.net/lixiang0522/article/details/7755059

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