python读写csv文件方法详细总结

python提供了⼤量的库，可以⾮常⽅便的进⾏各种操作，现在把python中实现读写csv⽂件的⽅法使⽤程序的⽅式呈现出来。在编写python程序的时候需要csv模块或者pandas模块，其中csv模块使不需要重新下载安装的，pandas模块需要按照对应的python版本安装。

在python2环境下安装pandas的⽅式是：

sudo pip install pandas

在python3环境下安装pandas的⽅式是：

sudo pip3 install pandas

1、使⽤csv读写csv⽂件⽅法总结

读⽂件的时候，打开⽂件，调⽤csv.reader()读取⽂件；对于读取之后的⽂件的内容，要把这些内容输⼊到另⼀个⽂件中保存，可以通过遍历读取的⽂件的每⼀⾏，然后使⽤csv_write.writerow()的⽅式写⼊到指定的⽂件。2、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8import csv

#读取csv⽂件

csv_file = csv.reader(open('../../data/capital/2010-Q4-cabi-trip-history-data.csv'))print(csv_file)

#添加newline可以避免⼀⾏之后的空格,这样需要在python3环境下运⾏out = open('../../data/capital/2010-Q4','a',newline='')csv_write = csv.writer(out,dialect='excel')

for item in csv_file: #print item

csv_write.writerow(item)

print(\"write over\")

上⾯的代码是传统的打开⽂件---读取⽂件---打开⽂件---关闭⽂件的⽅式进⾏⽂件读取和写⼊。在读取和写⼊的过程中分别调⽤了csv库的reader()和writer()3、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8import csv

#下⾯这种加了encoding的写法需要在python3环境下运⾏

csv_reader = csv.reader(open('../../data/capital/2011-Q1-cabi-trip-history-data.csv',encoding='utf-8'))

out = open('../../data/capital/a0','w',newline='')csv_writer = csv.writer(out,dialect='excel')

for row in csv_reader:

#输出的每⼀⾏是⼀个list,list中的每⼀个元素转换成了string类型 print(row)

csv_writer.writerow(row)

⽰例代码2的读写⽅式与⽰例代码1的⽅式基本相同，不同的是在⽰例代码2中打开⽂件的时候指定了打开时的编码⽅式，对于输出⽂件的打开⽅式也与⽰例代码1的⽅式有少量的差别，把写⼊⽅式右'a'改成了'w

4、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8import csv

#读取csv⽂件⽅式1

csvFile = open('../../data/capital/2011-Q3-cabi-trip-history-data.csv','r')reader = csv.reader(csvFile)

data = []

for item in reader:# print(item)

data.append(item)

#print(data)

csvFile.close()

#读取csv⽂件⽅式2

with open(\"../../data/capital/2011-Q3-cabi-trip-history-data.csv\ #读取csv⽂件,返回的是迭代类型 reader2 = csv.reader(csvFile) for item2 in reader2: print(item2)csvFile.close()

#从列表写⼊csv⽂件

#设置newline,否则两⾏之间会空⼀⾏

csvFile2 = open('../../data/capital/0001.csv','w',newline='')writer = csv.writer(csvFile2)m = len(data)for i in range(m):

writer.writerow(data[i])csvFile2.close()

#从字典写⼊csv⽂件

dic = {'张三':123,'李四':456,'王⼆娃':789}

csvFile3 = open('../../data/capital/0001.csv','w',newline='')writer2 = csv.writer(csvFile3)for key in dic: print(key)

# writer2.writerow([key,dic[key]])

csvFile3.close()

在上⾯的代码中提出了两种不同的打开csv⽂件和写⼊csv⽂件的⽅式。其中第⼀种打开⽅式与前⾯两种⾮常相似，不同之处是在这种⽅式中，打开⽂件的时候加⼊了读取⽅式，⽽前⾯两个⽰例代码没有加。另⼀种读取⽅式是采⽤python中独有的命名⽅式对打开⽂件命名，其他部分相似。在这个⽰例中，对列表和字典写⼊csv⽂件做了区分，分别提供了列表和字典写⼊csv⽂件的⽰例代码。

5、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8'''

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中的列名

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=TruedataFrame.to_csv('0001.csv',index=False,sep='')#pandas提供的读取csv的⽅法data = pd.read_csv('test.csv')'''

#===================================#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columns_name

writer.writerow([\"index\ #写⼊多⾏⽤writerows

writer.writerows([[1,2,3],[0,1,2],[4,5,6]])

#⽤reder读取csv⽂件

with open('test.csv','r') as csvFile: reader = csv.reader(csvFile) for line in reader: print line

这个⽰例代码提出了写⼊⼀⾏和写⼊多⾏的实现⽅式。6、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8import csv

with open('test.csv') as csvFile:

#readcsv = csv.reader(csvFile,delimiter='') readcsv = csv.reader(csvFile) #

rows= [row for row in readcsv] for row in readcsv:

rows= [row for row in reader] #print(row)#打印⼀⾏

print(row[0])#打印⼀⾏中的某个cell

print(row[0],row[1])#打印⼀⾏中的某个cell

print('=================')

with open('test.csv') as csvFile: readCSV = csv.reader(csvFile) cols1 = [] cols2 = [] cols3 = []

for row in readCSV: col1 = row[0] col2 = row[1] col3 = row[2]

cols1.append(col1) cols2.append(col2) cols3.append(col3)

print cols1print cols2print cols3

上⾯的代码⽰例提出了读取所有⾏的新写法，提出了读取某个cell和某⼀列的⽅式。7、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8import csv

#第⼀种⽅法:使⽤reader函数,接收⼀个可迭代的对象(⽐如csv⽂件),能返回⼀个⽣成器,就可以从其中解析出csv的内容.eg:下⾯的代码可以读取csv的全部内容,以⾏为单位with open('test.csv','rb') as csvFile: reader = csv.reader(csvFile) rows = [row for row in reader]

print rows

print('===========')

#提取其中某⼀列可以使⽤下⾯的⽅法with open('test.csv','rb') as csvFile: reader = csv.reader(csvFile)

column = [row[1] for row in reader]print column

print('======第⼆种⽅法======')

#第⼆种⽅法:使⽤DictReader,和reader函数类似,接收可迭代的对象,能返回⼀个可迭代的对象,能返回⼀个⽣成器,但是返回的每⼀个单元格都放在⼀个字典的值内,⽽这个字典的键则是这个单元格的标题.⽤下⾯的代码可以看到DictReader的结构:with open('test.csv','rb') as csvFile: reader = csv.DictReader(csvFile) column = [row for row in reader]print(column)

#使⽤CictReader读取csv的某⼀列,这样可以按照列的标题查询with open('test.csv','rb') as csvFile: reader = csv.DictReader(csvFile)

column = [row['a_name'] for row in reader]print column

上⾯的代码提出了读取整⾏和整列的新⽅式。另外提出了⼀种使⽤DictReader的⽅式按照列名读取的⽅式。8、使⽤csv读写csv⽂件⽰例代码

#encoding:utf-8

import csv

with open('test.csv','rb') as csvFile: reader = csv.reader(csvFile) for row in reader: print row

#向csv⽂件中写内容,这样写会把内容全部写到⼀个cell中with open('test1.csv','wb') as csvFile:

writer = csv.writer(csvFile,delimiter=' ',quotechar='|',quoting=csv.QUOTE_MINIMAL) writer.writerow(['a','4','5','6']) writer.writerow(['b','1','2','3']) writer.writerow(['c','9','8','7']) writer.writerow(['d','8','3','1'])

#向csv⽂件中写内容,下⾯的写法最终可以把每⼀列的内容放在⼀个cell中with open('test2.csv','wb') as csvFile:

writer = csv.writer(csvFile,dialect='excel') writer.writerow(['a','4','5','6']) writer.writerow(['b','1','2','3']) writer.writerow(['c','9','8','7']) writer.writerow(['d','8','3','1'])

上⾯的代码提出了可以把列表中的数据放⼊到不同cell的实现⽅式。