收集用户输入。在python中读取和写入文本文件

Question

基本上我想做的是让记事本列表显示在 python 中，这样用户就可以在不打开文件的情况下查看列表中的内容。我已经做到了。现在我想让用户输入他们想要的产品，然后保存它，然后打印出产品和价格。这是文本文件的样子：

000,67463528,50mm bolts,2.20
001,34512340,plain brackets,0.50
002,56756777,100mm bolts,0.20
003,90673412,l-shaped brackets,1.20
004,45378928,normal brackets,0.80
005,1638647,10mm bolts,0.10
006,14372841,plain brackets,1.29
007,29384754,200mm bolts,0.50
008,12345768,screwdriver,10.99

到目前为止，我可以在代码末尾添加产品，并且可以在某个行号处插入文本。我正在研究如何根据用户输入打印收据。我是 python 的新手，将其作为一种爱好来学习，任何帮助将不胜感激。谢谢！

这是python代码：

def search():
    gtin = input("What is the GTIN code? ")
    des = input("What is the name of the product? ")
    price = input ("What is the price of the product? ")
    position_str = input("What line do you want this inserted at? ")
    print("This is the list now: ")
    position = int(position_str)

    with open("task2.txt", "r") as a_file:
        data = a_file.readlines()

    data.insert(position, "00" + position_str + "," + gtin + "," + des + "," + price + "\n")

    data = "".join(data)

    with open("task2.txt",  "w") as a_file:
        a_file.write(data)

    input()

    with open('task2.txt','r')as Task2:
        print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format("\nNo.","GTIN-8","Item Name","Price"))
        for row in Task2:
            row=row.strip()
            eachItem=row.split(",")
            print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format(eachItem[0],eachItem[1],eachItem[2],eachItem[3]))
    print()



def add():
    print("The data you put here will be added onto the end ")
    gtin = input("What is the GTIN-8? ")
    des = input("What is the description? ")
    price = input("What is the price? ") #gets all the info they want to add
    print("This is the list now: ")

    with open("task2.txt","a") as a_file:
            a_file.writelines("   ," + gtin + "," + des + "," + price + "\n")
            a_file.close()
            print("Product has been added")

    with open('task2.txt','r')as Task2:
        print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format("\nNo.","GTIN-8","Item Name","Price"))
        for row in Task2:
            row=row.strip()
            eachItem=row.split(",")
            print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format(eachItem[0],eachItem[1],eachItem[2],eachItem[3]))
    print()



def reciept():

    print()



#this is the menu. this is where the user will make choices on what they do

def menu():
    print("What would you like to do?")

    with open('task2.txt','r')as Task2:
        print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format("\nNo.","GTIN-8","Item Name","Price"))
        for row in Task2:
            row=row.strip()
            eachItem=row.split(",")
            print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format(eachItem[0],eachItem[1],eachItem[2],eachItem[3]))
    print()


    print("1. Add a product onto a specific line number?")
    print("2. Or add a product onto the end?")
    print("3. Buy products and have them printed onto a reciept?")
    choice=int(input("Which one?: "))
    if choice==1:
        search()
    elif choice==2:
        add()
    elif choice==3:
        reciept()

menu()

Answer 1

要解决的问题和记录位置

首先，我似乎也无法完全复制你正在做的事情，我在某种程度上制定了自己的解决方案......

如果您提供了包含信息的文本文档，它可能有助于调试。

除此之外...我注意到如果您没有创建“task2.txt”文件，那么您就无法创建一个。

这可以通过Task2 = open("task2.txt", "w") 完成。 Input / Output Documentation for Python 2.7

其次，一些格式可以通过使用表达式来改进；即，

\t[标签]，

\n [换行符],

\r [返回],

因此您可以遵守 PEP-8 标准规则。 PEP-8 Documentation

好的，那就不碍事了，接下来您需要了解 open 和 with open 之间的区别...这里没有太大区别，只是 with open 会迫使您立即跳入循环。如果文档中没有信息，则会导致错误（这是我现在遇到的问题）。

将其存储为列表 (task2 = open([file], 'r') 更好，因为它允许您稍后使用它。您还应该运行检查以查看文件是否存在...

示例

第三，这里有一些技巧和窍门：

import os

boolCheckOnFile = os.path.isfile("[Location to File]\\task2.txt")
# Check if it exists
if boolCheckOnFile==False:
    # Create file, "w" for write
    task2Creation = open("[Location to File]\\task2.txt", "w")
    # Close the file to reopen and read it or write to it...
    task2Creation.close()

# Again "w" for write, "a" for append, "r" for read, "r+" for read/write...
task2 = open("[Location to File]\\task2.txt", "r+")

从这里，您可以通过执行str.write(information) 来写入文件。但最好在您真正完成文件后关闭文件...所以您对其所做的更改是永久的str.close()。

忠告，print() # print "()", you must fill it, so at least do a newline, like so:

print("\n")

我为解决一些初学者问题所做的工作

最后，下面是我的更正版本的迭代（仅适用于脚本的菜单部分）...

def menu():

    print("What would you like to do?")

    # Check if file exists
    if os.path.isfile('C:\\users\\[username]\\Desktop\\task2.txt')==False:
        # Create it and promptly close it, so it is in the correct location
        task1 = open('C:\\users\\[username]\\Desktop\\task2.txt','w')
        task1.close()

    # Open for read-write
    task2 = open('C:\\users\\[username]\\Desktop\\task2.txt','r+')

    # splits for new line break, making an array
    info = task2.read().split("\n")

    # Check to see if the file is empty
    if len(info) is not 0:
        print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format("\nNo.",
                                                                   "GTIN-8",
                                                                   "Item Name",
                                                                   "Price"))
        # Read each line of document
        for line in info:
            arrayOfItems = line.split(",")
            print('{0:<19}     {1:<19}     {2:<19}     {3:<19}'.format(arrayOfItems[0],
                                                                       arrayOfItems[1],
                                                                       arrayOfItems[2],
                                                                       arrayOfItems[3]))

    else:
        print('You have no items listed!')

    print("\n")


    print("1. Add a product onto a specific line number?")
    print("2. Or add a product onto the end?")
    print("3. Buy products and have them printed onto a reciept?")
    choice=int(input("Which one?: "))
    if choice==1:
        search()
    elif choice==2:
        add()
    elif choice==3:
        reciept()

menu()

祝你好运，享受制作 Python 脚本和程序的乐趣！有时很有趣也很有挑战性。我曾经站在你的立场上，请记住，随着你不断努力，它会变得更容易。

也：

查看其他 Stack Overflowers 的作品...有时可以通过查看其他人的作品和问题来解决像这样的简单解决方案...

Opening file for both reading and writing

Basic read and write

Lowercase examples plus reading and writing

Copying files for modifying documents and creating saves