CSV 读写

import csv

# 操作文件对象时，需要添加newline参数逐行写入，否则会出现空行现象
with open('eggs.csv', 'w', newline='') as csvfile:
    # delimiter 指定分隔符，默认为逗号，这里指定为空格
    # quotechar 表示引用符
    # writerow 单行写入，列表格式传入数据
    spamwriter = csv.writer(csvfile, delimiter=' ',quotechar='|')
    spamwriter.writerow(['www.biancheng.net'] * 5 + ['how are you'])
    spamwriter.writerow(['hello world', 'web site', 'www.biancheng.net'])


#想同时写入多行数据，需要使用 writerrows() 方法
with open('aggs.csv', 'w', newline='') as f:
    writer = csv.writer(f)
    # 注意传入数据的格式为列表元组格式
    writer.writerows([('hello', 'world'), ('I', 'love', 'you')])


#可使用 DictWriter 类以字典的形式读写数据
with open('names.csv', 'w', newline='') as csvfile:
    #构建字段名称，也就是key
    fieldnames = ['first_name', 'last_name']
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
    # 写入字段名，当做表头
    writer.writeheader()
    # 多行写入
    writer.writerows([{'first_name': 'Baked', 'last_name': 'Beans'},{'first_name': 'Lovely', 'last_name': 'Spam'}])
    # 单行写入
    writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})



#SV文件读取
import csv
with open('eggs.csv', 'r', newline='') as csvfile:
    spamreader = csv.reader(csvfile, delimiter=' ', quotechar='|')
    for row in spamreader:
        print(', '.join(row))

#csv.DictReader()
import csv
with open('names.csv', newline='') as csvfile:
    reader = csv.DictReader(csvfile)
    for row in reader:
        print(row['first_name'], row['last_name'])