python怎么在csv中写入

最常用的一种方法，利用pandas包

import pandas as pd
 
#任意的多组列表
a = [1,2,3]
b = [4,5,6]    
 
#字典中的key值即为csv中列名
dataframe = pd.DataFrame({'a_name':a,'b_name':b})
 
#将DataFrame存储为csv,index表示是否显示行名，default=True
dataframe.to_csv("test.csv",index=False,sep=',')

  a_name  b_name
0   1     4
1   2     5
2   3     6

同样pandas也提供简单的读csv方法

import pandas as pd
data = pd.read_csv('test.csv')

会得到一个DataFrame类型的data

另一种方法用csv包，一行一行写入

import csv
 
#python2可以用file替代open
with open("test.csv","w") as csvfile: 
    writer = csv.writer(csvfile)
 
    #先写入columns_name
    writer.writerow(["index","a_name","b_name"])
    #写入多行用writerows
    writer.writerows([[0,1,3],[1,2,3],[2,3,4]])

index  a_name  b_name
0      1      3
1      2      3
2      3      4

读取csv文件用reader

import csv
with open("test.csv","r") as csvfile:
    reader = csv.reader(csvfile)
    #这里不需要readlines
    for line in reader:
        print line

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