阅读python中的URL

Question

我需要帮助来理解此代码。我无法理解循环。有人可以分解并解释吗？ “ i = 0”在此程序中代表什么。这是示例代码。我的作业是为丢失和无效的数据添加错误处理。我非常感谢。谢谢！

    import os
import urllib.request as ur

def process_file(link):
    data = ur.urlopen(link)
    fields = ["TITLE", "ARTIST", "COUNTRY", "COMPANY", "PRICE", "YEAR"]
    title = []
    artist = []
    country = []
    company = []
    price = []
    year = []
    for line in data:
        line = line.decode('utf-8')
        line = line.lstrip()
        line = line.rstrip()

        tag = ""
        value = ""
        i = 0
        while i < len(line):

            if line[i] == '<':
                i = i + 1
                while i < len(line) and line[i] != '>':
                    tag += line[i]
                    i = i + 1

                if tag not in fields:
                    break;

                i = i + 1;

            while i < len(line) and line[i] != '<':

                value += line[i]
                i = i + 1
            break;

        if tag == "TITLE":
            title.append(value)
        elif tag == "ARTIST":
            artist.append(value)
        elif tag == "COUNTRY":
            country.append(value)
        elif tag == "COMPANY":
            company.append(value)
        elif tag == "PRICE":
            price.append(float(value))
        elif tag == "YEAR":
            year.append(int(value))
    return title,artist,country,company,price,year

def display(title, artist, country, company, price ,year):
    for i in range(len(title)):
        print(title[i] , " - ", artist[i], " - ", country[i], " - ", company[i], " - ",  price[i],  " - ", year[i])
    return 

def calculate_average(price):
    sum = 0.0
    if len(price) == 0:
        return sum
    for value in price:
        sum = sum + value
    return sum/len(price)

if __name__ == '__main__':

    link = "https://www.w3schools.com/xml/cd_catalog.xml"
    title, artist, country, company, price ,year = process_file(link)
    display(title, artist, country, company, price ,year)
    print((len(title)), " items - $" , round(calculate_average(price),2), " average price")

Answer 1

我可以解释一下。

 I = 0

这将创建一个名为I的新变量，并将其设置为零。

while I < Len (line)

这意味着在此循环中执行的所有代码将继续执行，直到我大于行数为止。如您所见，在循环中，它将i加1。这意味着直到循环结束还需要几秒钟。