如何查找和修复错误

Question

我有一个任务来修复程序中的错误，我不知道该怎么做，从哪里开始。你知道吗

#this function takes, as input, a list of numbers and returns the list with the following changes:
# if the original value in the list is positive, the value is doubled
# if the original value in the list is negative, the value is tripled
# if the value in the list is 0, then the value is replaced with the string “zero”
# for example, the result from timesTwo([1, 5, -2, 4, 0, -5, 3]) should be [2,10,-6,8,’zero’,-15,6]
def timesTwo(myList):
    counter = 0
    while (counter <= len(myList)):
        if (mylist(counter) > 0:
            myList[counter] = myList[counter * 2]
        counter = counter + 1
        elif (myList[counter] < 0):
            myList[counter] = myList[counter * 3]
        counter = counter + 1
        else:
            myList[counter] = “zero”
    return myList

Answer 1

要查找逻辑错误，请尝试编写一些测试。您知道函数应该如何运行，因此请尝试考虑各种输入，看看函数是否提供了预期的输出。你知道吗

例如

myList = [1,2,3]
expectedList = [2,4,6]

result = timesTwo(myList)

print( "The lists are the same size: " + len(expectedList) == len(result) )
for( i = 0, i < len(expectedList), i++ ):
    print( "The element at position " + i + " is " + result[i] + " and should be " expectedList[i] )

语法和异常应该告诉您错误来自哪一行。你知道吗

Answer 2

为了补充其他人所说的内容，您还可以测试程序所说的应该做的事情。例如，只要给它一个由几个正数组成的列表，比如[1，2，3]，并确保输出是[3，6，9]。你知道吗

Answer 3

什么样的错误？你知道吗

如果它们是例外，那就很容易了。Python会告诉您异常发生在哪一行，并提供完整的回溯。你知道吗

如果它们是逻辑错误，那就更难了。非常自由的使用pdbpython调试器将有助于调试打印陈述。只是一般的分析方法。如果结果不是您希望的结果，则在必要时使用pdb逐行遍历整个程序