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[【原文链接】Python----如何处理csv文件即csv模块的用法](http://devops-dev.com/article/146)

[TOC]
### csv写文件
* csv.writer(f) 获取csv的write
* writerow 写入一行数据
* writerows 写入多行数据
* 注意打开文件的时候将 newline设置为“”，否则写的csv会存在空行

```python
import csv

def main():
    csv_file= "demo.csv"
    head=["name","age","sex"]
    data1=["zhangsan",20,"man"]
    data2=[
        ["lisi",22,"man"],
        ["wangmei",18,"woman"]
    ]
    with open(csv_file,"a+",encoding="utf-8",newline="") as f:
        csv_writer=csv.writer(f)
        csv_writer.writerow(head)
        csv_writer.writerow(data1)
        csv_writer.writerows(data2)

if __name__=="__main__":
    main()
```

### csv读文件

```python
import csv

def main():
    csv_file= "demo.csv"
    with open(csv_file,"r",encoding="utf-8",newline="") as f:
        ctx=csv.reader(f)
        for row in ctx:
            print(row)

if __name__=="__main__":
    main()
```

### csv 写入数据为字典数据
   * 注意初始化DictWriter的是就需要指定fieldnames

```python
import csv

def main():
    csv_file= "demo.csv"
    head=["name","age","sex"]
    data1={"name":"zhangsan","age":20,"sex":"man"}
    data2=[
        {"name":"lisi","age":22,"sex":"man"},
        {"name":"wangmei","age":18,"sex":"woman"}
    ]
    with open(csv_file,"a+",encoding="utf-8",newline="") as f:
        csv_writer=csv.DictWriter(f,fieldnames=head)
        csv_writer.writerow(data1)
        csv_writer.writerows(data2)

if __name__=="__main__":
    main()
```

### csv读取数据为字典数据
   * 读取的时候初始化DictReader的时候不需要指定fieldnames，会自动将第一行作为fieldnames字段，然后读取出来

```python
import csv

def main():
    csv_file= "demo.csv"
    with open(csv_file,"r",encoding="utf-8",newline="") as f:
        ctx=csv.DictReader(f)
        for elem in ctx:
            print(elem)

if __name__=="__main__":
    main()
```

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