1、CSV 文件存储
1.1 写入
简单示例
import csv
with open('data.csv', 'a') as csvfile:
writer = csv.writer(csvfile) # 初始化写入对象，传入文件句柄
writer.writerow(['id', 'name', 'age']) # 调用 writerow() 方法传入每行的数据
writer.writerow(['1', 'rose', '18'])
writer.writerow(['2', 'john', '19'])
以文本方式打开，分隔符默认为逗号（,）：
id,name,age
1,rose,18
2,john,19
修改默认分隔符：
writer = csv.writer(csvfile, delimiter=' ') # 以空格为分隔符
同时写入多行：
# 此时参数为二维列表
writer.writerow([['1', 'rose', '18'], ['2', 'john', '19']])
避免出现空行，可以在写入时加 newline=''：
with open("test.csv", "a+", newline='') as csvfile:
如果数据源是字典
import csv
with open('data1.csv', 'a') as csvfile:
fieldnames = ['id', 'name', 'age'] # 定义表头
writer = csv.DictWriter(csvfile, fieldnames=fieldnames) # 初始化一个字典，将文件句柄和表头传入
writer.writeheader() # 写入表头
writer.writerow({'id': '1', 'name': 'rose', 'age': 18}) # 写入表格中具体内容
编码问题，需要指定 open() 函数编码格式：
open('data.csv', 'a', encoding='utf-8')
另外 pandas 库的 DataFrame 对象的 to_csv() 方法也可以将数据写入 csv 中。
1.2 读取
import csv
with open('data1.csv', 'r') as csvfile:
reader = csv.reader(csvfile)
for row in reader:
print(row)
结果如下：
['id', 'name', 'age']
['1', 'rose', '18']
Tips：如果有中文需要指定文件编码
pandas 库的 read_csv() 方法
import pandas as pd
df = pd.read_csv('data.csv')
print(df)
运行结果如下：
id name age
0 1 rose 18
1 2 john 19
1.3 避免重复插入表头
#newline的作用是防止每次插入都有空行
with open("test.csv", "a+", newline='') as csvfile: # 必须使用 a+，追加方式
writer = csv.writer(csvfile)
#以读的方式打开csv 用csv.reader方式判断是否存在标题。
with open("test.csv", "r", newline="") as f:
reader = csv.reader(f)
if not [row for row in reader]:
writer.writerow(["型号", "分类"])
writer.writerows([[keyword, miaoshu]])
else:
writer.writerows([[keyword, miaoshu]])
示例
爬取一下该网站的所有评论：https://www.bestbuy.ca/en-ca/product/hp-hp-officejet-pro-6968-all-in-one-inkjet-printer-with-fax-6968/10441056/review
import requests
import time
import csv
headers = {
"User-Agent": "Mozilla/5.0 (iPhone; CPU iPhone OS 11_0 like Mac OS X) AppleWebKit/604.1.38 (KHTML, like Gecko) "
"Version/11.0 Mobile/15A372 Safari/604.1",
"Referer": "https://www.bestbuy.ca/en-ca/product/hp-hp-officejet-pro-6968-all-in-one-inkjet-printer-with-fax-"
"6968/10441056/review"
}
def get_content(url):
"""爬取数据"""
res = requests.get(url=url, headers=headers)
# print(res.status_code)
return res.json()
def parse_res(res):
"""解析数据"""
csv_data = {}
# print(res, type(res))
data = res["reviews"]
for i in data:
csv_data["title"] = i["title"]
csv_data["comment"] = i["comment"]
csv_data["publish"] = i["reviewerName"]
csv_data["publish_time"] = i["submissionTime"]
print(csv_data)
save_data(csv_data)
def save_data(csv_data):
"""存储数据"""
with open('data.csv', 'a+', newline='') as csvfile:
# 以读的方式打开 csv，判断表格是否有数据
with open('data.csv', 'r', newline='') as f:
reader = csv.reader(f)
fieldnames = ['title', 'comment', 'publish', 'publish_time']
writer = csv.DictWriter(csvfile, fieldnames=fieldnames) # DictWriter： 字典
if not [row for row in reader]:
writer.writeheader()
writer.writerow(csv_data)
else:
writer.writerow(csv_data)
if __name__ == '__main__':
for i in range(1, 11):
url = 'https://www.bestbuy.ca/api/v2/json/reviews/10441056?source=all&lang=en-CA&pageSize=10&page=%s' \
'&sortBy=date&sortDir=desc' % i
res = get_content(url)
time.sleep(2)
parse_res(res)
参考文章：https://blog.csdn.net/qq_41817302/article/details/88680886
1.4 避免读取第一行表头
import csv
l = []
FileObj = open('t.csv')
readerObj = csv.reader(FileObj)
for row in readerObj:
if readerObj.line_num == 1: # readerObj.line_num 会返回 csv 文件的行数
continue
l.append(row)
print(l)
FileObj.close()
[['1', 'rose', '18'], ['2', 'lila', '19']]
1.5 按字典格式读取
import csv
# 编码问题，请添加 encoding = 'utf-8'。pandas 库可以调用 DataFrame 对象的 to_csv() 方法写入 csv 中
with open('C:\\Users\\hj\\Desktop\\data2.csv', 'w') as f:
# writer = csv.writer(f)
# writer.writerow(['id', 'name', 'age'])
# writer.writerow([1, 'rose', 18])
# writer.writerow([2, 'tom', 19])
# 存储字典
fieldnames = {'id', 'name', 'age'}
writer = csv.DictWriter(f, fieldnames=d)
writer.writeheader()
writer.writerow({'id': 1, 'name': 'rose', 'age':18})
writer.writerow({'id': 2, 'name': 'lina', 'age':19})
writer.writerow({'id': 3, 'name': 'john', 'age':20})
2. JSON 文件存储
2.1 读取 JSON
import json
s = '''
[{
"name": "rose",
"gender": "female",
"age": "18"
}]
'''
data = json.loads(s)
print(data)
print(type(data))
运行结果如下：
[{'name': 'rose', 'gender': 'female', 'age': '18'}]
<class 'list'> # 因为最外层是列表
读取 JSON 文件
with open('data.json', 'r') as f:
s = f.read()
data = json.loads(s)
print(data)
2.2 输出 JSON
import json
data = [{
"name": "rose",
"gender": "female",
"age": "18"
}]
with open('data.json', 'a') as f:
f.write(json.dumps(data))
缩进 2 个字符，这样结构更清晰：
with open('data.json', 'a') as f:
f.write(json.dumps(data, indent=2))
运行结果如下：
[
{
"name": "rose",
"gender": "female",
"age": "18"
}
]
如果输出的包含中文，须臾指定参数 ensure_ascii=False，否则默认转换为 Unicode 字符：
with open('data.json', 'a') as f:
f.write(json.dumps(data, indent=2, ensure_ascii=False))
