python_csv
'''
csv文件的读取
'''
import csv # 导入csv包
reader 读取csv文件
with open("bad_url.csv", 'r') as url_file:
rows = csv.reader(url_file)
for row in rows:
print(type(row))
print(row)
'''
结果：
['ID', 'URL']
['1', 'www.baidu.com']
['2', 'www.facebook.com']
['3', 'www.youku.cm']
['4', 'www.taobao.com']
['5', 'www.tengcen.com']
['6', 'www.zhihu.com']
'''
writer 写入csv文件
with open("bad_url.csv", 'a',newline='') as url_file: #w可写但是会删掉然来的数据，a表示追加
writer = csv.writer(url_file)
writer.writerow(['7', 'www.youtube.com'])
writer.writerow(['6', 'www.zhihu.com'])
'''
7, www.youtube.com
6, www.zhihu.com
#中间会有一个空行,open参数加入’newline=''‘就可以避免
'''
# 字典形式读写文件
# csv模块还提供了 csv.DictReader() 和 csv.DictWriter()
# csv.DictWriter
with open('bad_url.csv', 'w') as url_file:
fieldnames = ['first_name', 'last_name'] # 指定标题列
writer = csv.DictWriter(url_file, fieldnames=fieldnames)
writer.writeheader()
writer.writerow({'first_name': 'Baked', 'last_name': 'Beans'})
writer.writerow({'first_name': 'Lovely', 'last_name': 'Spam'})
writer.writerow({'first_name': 'Wonderful', 'last_name': 'Spam'})
# csv.DictReader
with open('bad_url.csv') as url_file:
reader = csv.DictReader(url_file)
for row in reader:
print(row['first_name'], row['last_name']) # 根据标题列定义的数据取行内容
