從列表中刪除元素

Question

我無法從lists中刪除元素。 發送e-mail時，我想從urls[]和prices[]中刪除相關元素。

前任。 if email has: like a url an Iphone X and like a price 500€ and it had been sent, i want to "rewrite" the elements in urls[] and prices[] lists removing iphone's url and 500€

import requests
from bs4 import BeautifulSoup
import smtplib
import time

#   https://www.amazon.it/Corsair-Vengeance-Memorie-Desktop-Prestazioni/dp/B0143UM4TC
#   https://www.amazon.it/AMD-Ryzen-5-3600-Processori/dp/B07STGGQ18
#   https://www.amazon.it/Apple-iPhone-Grigio-Siderale-Ricondizionato/dp/B07985C44N

urls = []
prices=[]
all_product = []
n = int(input("Inserisci il numero di prodotti: "))

#agginge il link da controllare
print("\nInserisci i link:")
for i in range(0, n): 
    link = str(input()) 
    urls.append(link)    

#aggiunge il realtivi prezzi ai link
print("\nInserisci i prezzi:")
for i in range(0, n): 
    money = int(input()) 
    prices.append(money) 

#headers per i diversi motori di ricerca
headers = {'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0 Chrome/83.0.4103.97 Safari/537.36'}

def check_price():
    for url, price in zip(urls, prices):
        soup  = BeautifulSoup(requests.get(url, headers=headers).content, 'lxml')
        title = soup.find(id='productTitle').get_text(strip=True)    
        try:
            products = soup.find(id='priceblock_ourprice').get_text()
            fix_string = products.replace(",", ".")      
            converted_price = float(fix_string[0:5])
            all_product.append(converted_price)
            money_saved=converted_price-price
            if (converted_price<=price): 
                 #send email
                remove_link=str(url)
                remove_price=price
                if(urls.index(remove_link)&prices.index(remove_price)):
                    urls.pop((urls.index(remove_link)))
                    prices.pop(prices.index(remove_price))
         except AttributeError:
            print ("Prezzo non trovato, controlla se il prodotto ha un prezzo esposto")
    print(all_product)

Answer 1

在 Python 中，從用於for... in....的列表中刪除不是一個好主意，因為當您刪除元素時，其他元素會被移動（因此下一個元素代替已刪除的元素）但for不會知道它，它會跳轉到列表中的下一個元素，並跳過已移動到已刪除元素位置的元素。

最好在循環之前創建空列表（ keep_urls = [] ），在循環 append 到要保留的列表元素（ keep_urls.append(url) ），然后在循環之后將此列表分配給舊變量（ urls = keep_urls ）。 之后，您可以再次運行它，它將使用沒有刪除元素的列表。

這段代碼顯示了我的看法。

順便說一句：因為使用input()添加數據很長而且很無聊，所以我添加了從文件中讀取數據的代碼。

import requests
from bs4 import BeautifulSoup
import smtplib
import time

# --- functions ---

def ask_for_data():
    urls = []
    prices = []

    n = int(input("Inserisci il numero di prodotti: "))

    #agginge il link da controllare
    print("\nInserisci i link:")

    for i in range(n): 
        link = input()
        urls.append(link)    

    #aggiunge il realtivi prezzi ai link
    print("\nInserisci i prezzi:")

    for i in range(n): 
        money = input()
        prices.append(money) 

    return urls, prices

def read_data():
    with open('urls.txt') as fh:
        text = fh.read()
        urls = text.split('\n')

    with open('prices.txt') as fh:
        text = fh.read()
        prices = text.split('\n')

    return urls, prices

def write_data(urls, prices):
    with open('urls.txt', 'w') as fh:
        text = "\n".join(urls)
        fh.write(text)

    with open('prices.txt', 'w') as fh:
        text = "\n".join(prices)
        fh.write(text)

def send_email(url, price, converted_price):
    #money_saved = converted_price-price
    print('TODO: send mail with', url, price, converted_price)

# --- main ---

# - start -
#urls, prices = ask_for_data()
urls, prices = read_data()

#headers per i diversi motori di ricerca
headers = {
    'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0 Chrome/83.0.4103.97 Safari/537.36'
}

while True:

    # - before loop -
    keep_urls = []
    keep_prices = []
    all_products = []

    # - loop -
    for url, price in zip(urls, prices):
        r = requests.get(url, headers=headers)
        #print(r.status_code)
        soup  = BeautifulSoup(r.content, 'lxml')
        title = soup.find(id='productTitle').get_text(strip=True)    
        try:
            products = soup.find(id='priceblock_ourprice').get_text()
            fix_string = products.replace(",", ".")      
            converted_price = float(fix_string[0:5])

            all_products.append(converted_price)

            if converted_price <= price: 
                send_email(url, price, converted_price)
            else:
                keep_urls.append(url)
                keep_prices.append(price)

         except AttributeError as ex:
            print('Ex:', ex)
            print("Prezzo non trovato, controlla se il prodotto ha un prezzo esposto")

    # - loop -
    urls = keep_urls
    prices = keep_prices

    print(all_products)

    time_sleep(60)

# - end -
write_data(urls, prices)