4.1.如何读写csv数据

 爬取豆瓣top250书籍

import requests
import json
import csv
from bs4 import BeautifulSoup

books = []

def book_name(url):
    res = requests.get(url)
    html = res.text
    soup = BeautifulSoup(html, 'html.parser')
    items = soup.find(class_="grid-16-8 clearfix").find(class_="indent").find_all('table')

    for i in items:
        book = []
        title = i.find(class_="pl2").find('a')
        book.append('《' + title.text.replace(' ', '').replace('\n', '') + '》')

        star = i.find(class_="star clearfix").find(class_="rating_nums")
        book.append(star.text + '分')

        try:
            brief = i.find(class_="quote").find(class_="inq")
        except AttributeError:
            book.append('”暂无简介“')
        else:
            book.append(brief.text)

        link = i.find(class_="pl2").find('a')['href']
        book.append(link)

        global books
        books.append(book)

        print(book)

    try:
        next = soup.find(class_="paginator").find(class_="next").find('a')['href']
    # 翻到最后一页
    except TypeError:
        return 0
    else:
        return next


next = 'https://book.douban.com/top250?start=0&filter='
count = 0

while next != 0:
    count += 1
    next = book_name(next)
    print('-----------以上是第' + str(count) + '页的内容-----------')

csv_file = open('D:/top250_books.csv', 'w', newline='', encoding='utf-8')
w = csv.writer(csv_file)
w.writerow(['书名', '评分', '简介', '链接'])
for b in books:
    w.writerow(b)

结果

把评分为9.0的书籍保存到book_out.csv文件中

'''
1.爬取豆瓣评分排行前250本书,保存为top250.csv
2.读取top250.csv文件，把评分为9.0以上的书籍保存到另外一个csv文件中
'''

import csv

#打开的时候必须用encoding='utf-8'，否则报错
with open('top250_books.csv', encoding='utf-8') as rf:
    reader = csv.reader(rf)
    #读取头部
    headers = next(reader)
    with open('books_out.csv', 'w', encoding='utf-8') as wf:
        writer = csv.writer(wf)
        #把头部信息写进去
        writer.writerow(headers)

        for book in reader:
            #获取评分
            score = book[1]
            #把评分大于9.0的过滤出来
            if score and float(score) >= 9.0:
                writer.writerow(book)

 4.2.如何读写excel

 安装两个库

pip install xlrd xlwt

读取excel

#4.2.如何读取excel

import xlrd

book = xlrd.open_workbook('demo.xlsx')

sheet = book.sheet_by_index(0)
#获取有多少行多少列
print(sheet.nrows)   #4
print(sheet.ncols)   #4

print(sheet.cell(0,0))          #text:'姓名'
print(sheet.cell_value(0,0))    #姓名

print(sheet.row_values(0))      #['姓名', '语文', '数学', '外语']
print(sheet.row_values(1,1))    #[95.0, 99.0, 96.0]

求分数的总和

#4.2.如何读写excel

import xlrd, xlwt

rbook = xlrd.open_workbook('demo.xlsx')
rsheet = rbook.sheet_by_index(0)

k = rsheet.ncols
#在最后添加一列 ‘总分’
rsheet.put_cell(0,k,xlrd.XL_CELL_TEXT, '总分', None)

for i in range(1,rsheet.nrows):
    #求分数总和
    t = sum(rsheet.row_values(i, 1))
    rsheet.put_cell(i,k,xlrd.XL_CELL_NUMBER,t,None)

wbook = xlwt.Workbook()
wsheet = wbook.add_sheet(rsheet.name)

for i in range(rsheet.nrows):
    for j in range(rsheet.ncols):
        wsheet.write(i,j,rsheet.cell_value(i,j))

wbook.save('out.xlsx')

 结果