Python 文件 I/O 和列表有问题

Question

所以我必须用列表和输入输出文件做一个 Python 编程作业，但我卡住了。我必须查找具有名称、颜色和周长的三角形。三角形位于 .txt 文件中，如下所示：

Triangle1,red,0,0,0,1,1,0
Triangle2,blue,1,0,0,1,0,0
GeorgeJetson,BLUE,20.1,10.5,23,5,6,33.3
Triangle4,BlUe,10,10,20,20,0,0
Triangle2,red,1,1,0,1,0,0
Gusty,orange,0,0,0,2,2,2
Gusty,red,0,0,0,2,2,2
triangle2,orange,0,0,0,2,2,2

到目前为止我的代码是这样的：

from math import sqrt

def peri(x1,y1,x2,y2,x3,y3):
    side1 = sqrt(((x1-x2)**2)+((y1-y2)**2))
    side2 = sqrt(((x2-x3)**2)+((y2-y3)**2))
    side3 = sqrt(((x1-x3)**2)+((y1-y3)**2))
    p = side1 + side2 + side3
    return p

def main():
    # Handshake
    print("This program performs database processing.")
    # Prompt for input and output file names
    infileName = input("Enter input file name: ")
    outfileName = input("Enter output file name: ")

    # Open input file name and read it
    infile = open(infileName,"r")

    # Read file, create triangle list
    trilist = []
    for line in infile:
        name,color,x1,y1,x2,y2,x3,y3 = line.split(",")
        x1 = eval(x1)
        y1 = eval(y1)
        x2 = eval(x2)
        y2 = eval(y2)
        x3 = eval(x3)
        y3 = eval(y3)
        perimeter = peri(x1,y1,x2,y2,x3,y3)
        triangle = name,color,perimeter
        trilist.append(triangle)

    # Close input file
    infile.close()

    LowerCaseOutfile = False
    AscendingOutfile = False
    print("")
    print("Commands:")
    print("perimeterbyname: Display triangle perimenters by name")
    print("perimeterbycolor: Display triangle perimenters by color")
    print("namebycolor: Display triangle names by color")
    print("colorbyname: Display triangle colors by name")
    print("lowercase: Display triangle names and colors in lowercase")
    print("ascending: Display triangle perimeters in ascending order")
    print("quit: Quit the program")
    print("")
    userInput = input("Enter a command: ")
    while userInput != "quit":
        if userInput == "perimeterbyname":
            triname = input("Enter a triangle name: ")
            for triangle in trilist:
                if triname == name:
                    print(triangle)
                else:
                    print("Invalid name")

        print("")
        print("Commands:")
        print("perimeterbyname: Display triangle perimenters by name")
        print("perimeterbycolor: Display triangle perimenters by color")
        print("namebycolor: Display triangle names by color")
        print("colorbyname: Display triangle colors by name")
        print("lowercase: Display triangle names and colors in lowercase")
        print("ascending: Display triangle perimeters in lascending order")
        print("quit: Quit the program")
        print("")
        userInput = input("Enter a command: ")


    # Open output file name and write it
    outfile = open(outfileName, "w")

    # Write to the output file
    print(trilist, file = outfile)

    # Close output file
    outfile.close()

    print("Triangles have been written to", outfileName)


main()

我无法从 if 语句的列表中获取三角形的名称。 Python 无法识别变量 "name"。帮忙？

Answer 1

我猜您是在谈论 while 在循环中仅当它与用户输入匹配时才打印出三角形。 "name" 无效的原因是 python 不存储您在创建三角形列表时使用的变量，仅存储它们的值。因此，当您再次读取它们时，它只是一个值。

因此，每个三元组（元组列表）是： [("name","color",perimeter),("name","color",perimeter)] 其中 "name", "color" 和 perimeter 是实际的每个三角形的值。

现在您可以将元组的值提取到单独的变量中：

name, color, perimeter = triangle

在你的 for 循环中，然后按照你的预期使用变量，或者直接手动索引元组：

name = triangle[0]

现在，为了将它们组合在一起，您实际上可以用两种方式编写 for 循环：

        # leave triangle as a tuple
        for triangle in trilist:
            if triname == triangle[0]:
                print(triangle)
            else:
                print("Invalid name")

或：

        # assign elements of tuple to separate variables
        for name,color,perimeter in trilist:
            if triname == name:
                print(triangle)
            else:
                print("Invalid name")

Python 文件 I/O 和列表有问题

Trouble with Python file I/O and lists

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