Python中CSV文件(逗号分割)实战操作指南

MariaDB [test]> select * from 表名 into outfile "/tmp/test.csv" fields terminated by ","; 

[root@python _test]# vim test.csv                      ###可以发现复制进去的是以空格为分隔符
id      username        passwd  age
1       dream1  123     21
2       dream2  456     22
3       dream3  789     23

### 把空格替换为逗号
[root@python _test]# sed -i 's/\s\+/,/g' test.csv

[root@python _test]# vim _test.py 
#!/usr/bin/env python
#coding:utf-8
import csv
with open('test.csv', encoding="utf-8") as f:
    reader = csv.reader(f)
    print(reader)
    print(list(reader))

### 查看结果
[root@python _test]# python _test.py
<_csv.reader object at 0x7f54d9a01eb8>
[['id', 'username', 'passwd', 'age'], ['1', 'dream1', '123', '21'], ['2', 'dream2', '456', '22'], ['3', 'dream3', '789', '23']]

[root@python _test]# vim _test.py 
#!/usr/bin/env python
#coding:utf-8
import csv
with open('test.csv', encoding="utf-8") as f:
    reader = csv.reader(f)
    for i in reader:
        print(reader.line_num, i)
 
 ### 查看结果
[root@python _test]# python _test.py
1 ['id', 'username', 'passwd', 'age']
2 ['1', 'dream1', '123', '21']
3 ['2', 'dream2', '456', '22']
4 ['3', 'dream3', '789', '23']

[root@python _test]# vim _test.py
#!/usr/bin/env python
#coding:utf-8
import csv
with open('test.csv', encoding="utf-8") as f:
    reader = csv.reader(f)
    ### 这个就是我们得表头
    next(reader)
    for i in reader:
        print(reader.line_num, i)
        
### 查看结果
[root@python _test]# python _test.py    
2 ['1', 'dream1', '123', '21']
3 ['2', 'dream2', '456', '22']
4 ['3', 'dream3', '789', '23']

[root@python _test]# vim _test.py
#!/usr/bin/env python
#coding:utf-8
import csv
with open('test.csv', encoding="utf-8") as f:
    reader = csv.DictReader(f)
    ### 表头
    print (reader.fieldnames)
    print (reader,type(reader))
    for i in reader:
        print (i)
        
### 查看结果
[root@python _test]# python _test.py
['id',  'username',  'passwd',  'age']
<csv.DictReader object at 0x7f3b02213a20> <class 'csv.DictReader'>
OrderedDict([('id', '1'), ('username', 'dream1'), ('passwd', '123'), ('age', '21')])
OrderedDict([('id', '2'), ('username', 'dream2'), ('passwd', '456'), ('age', '22')])
OrderedDict([('id', '3'), ('username', 'dream3'), ('passwd', '789'), ('age', '23')])

[root@python _test]# vim _test.py
#!/usr/bin/env python
#coding:utf-8
import csv
with open('test.csv', encoding="utf-8") as f:
    reader = csv.DictReader(f)
    for i in reader:
        print (i['id'])
        
### 查看结果
[root@python _test]# python _test.py
1
2
3

[root@python _test]# vim _test.py
#!/usr/bin/env python
#coding:utf-8
import csv
li = [["id","user","性别"],["1","dreamya1","男"],["2","dreamya2","女"]]
with open('user.csv', 'w', newline='') as f:
    writer = csv.writer(f)
    for i in li:
        writer.writerow(i)

### 查看结果
[root@python _test]# python _test.py 
[root@python _test]# cat user.csv 
id,user,性别
1,dreamya1,男
2,dreamya2,女

[root@python _test]# sz user.csv 

[root@python _test]# vim _test.py
import csv
#coding:utf-8
headers = ['id', 'username','passwd']
li = [{'id':'1','username':'dream1','passwd':'123'},
        {'id':'2','username':'dream2','passwd':'456'},
        ]
        
with open('user.csv', 'w', newline='') as f:
    ### 表头传入
    writer = csv.DictWriter(f, headers)
    writer.writeheader()    
    ### 一行一行写入
    for i in li:
        writer.writerow(i)
        
    ### 直接把li写入（多行）
    writer.writerows(li)

### 查看结果
[root@python _test]# python _test.py
[root@python _test]# cat user.csv 
id,username,passwd
1,dream1,123
2,dream2,456
1,dream1,123
2,dream2,456

[root@python _test]# sz user.csv