Question

我试图创建一个递归函数，检查等级是否可以转换为浮点数，然后检查以确保等级在0到100之间。我的逻辑为什么这将起作用：< / p>

检查等级是否可以转换为浮动。
如果无法将其转换为浮点数，则用户会收到错误消息，必须输入新等级，并且gradeChecker会再次检查。
如果可以将其转换为浮动，则gradeChecker会检查它是否在0到100之间
如果等级介于0到100之间，则会将成绩附加到“作业”字典。
如果等级不在0到100之间，则用户会给出新等级，然后将其传回函数，从第1步开始重复。

你能告诉我这段代码是如何遵循这个逻辑的吗？

def gradeChecker(grade):
    while True:
        try:
            grade = float(grade)        
            while (grade < 0) or (grade > 100):
                print("Sorry, your grade must be between 0 and 100.")
                grade = input("What grade did you receive on: %s? " % assignment)
                gradeChecker(grade)
        except:
            print("Sorry, that's an invalid input. Please only use numbers and decimal points!")
            grade = input("What grade did you receive on: %s? " % assignment)
        else:
            break
    Assignments[assignment].append(grade)

编辑：缩进已修复！

供参考，以下是我用来将成绩传递给gradeChecker的全部代码。

import collections #We import collections so we can use an ordered dictionary
Assignments = collections.OrderedDict() #We create an ordered dictionary called 'Assignments'
#We have to add each assignment to our dictionary individually because it's an ordered dictionary
#You can't convert a regular dictionary, which is unordered, to an ordered dictionary
#If you used a regular dictionary, when looping through the assignments they would be displayed at random
Assignments['Exam 1'] = [0.2] #We add the assignment and the weight to the dictionary
Assignments['Exam 2'] = [0.2] #We add the assignment and the weight to the dictionary
Assignments['Exam 3'] = [0.2] #We add the assignment and the weight to the dictionary
Assignments['Homework'] = [0.2] #We add the assignment and the weight to the dictionary
Assignments['LQR'] = [0.1] #We add the assignment and the weight to the dictionary
Assignments['Final'] = [0.1] #We add the assignment and the weight to the dictionary

#We have to define our grade checker before it is called so that it can be used to verify users inputs

def gradeChecker(grade): #Used to verify that a users grades are in-between 0 and 100
    while True:
        try:
            grade = float(grade)        
            while (grade < 0) or (grade > 100):
                print("Sorry, your grade must be between 0 and 100.")
                grade = input("What grade did you receive on: %s? " % assignment)
                gradeChecker(grade)
        except:
            print("Sorry, that's an invalid input. Please only use numbers and decimal points!")
            grade = input("What grade did you receive on: %s? " % assignment)
        else:
            break
    Assignments[assignment].append(grade) #We append the grade to the assignment to be used with it's weight for the final grade calculation

#INPUT

for assignment in Assignments.keys(): #We loop through every assignment in our  Assignments dictionary
    grade = input("What grade did you receive on: %s? " % assignment) #We ask the user to enter their grade
    gradeChecker(grade) #We check to see if their grade is valid by passing their input through the gradeChecker function

Answer 1

这里使用递归和循环是多余的。此外，循环应该优先于正常的递归＃39;像Python这样的语言（即不是Lisp），除非您正在处理像树这样的固有递归数据结构。

鉴于你从未说过为什么你需要首先使用递归，我建议使用这样的东西：

Assignments

注1 。我没有测试上面的代码，但是它应该让你对如何构造这个函数有一个大概的了解。

注2 。您应该避免在函数中修改try，这是一个不必要的副作用。最好将其卸载到主代码中。

注3 。从技术上讲，我的代码中的except .. Message是基于异常的逻辑的一个例子，这不是一件好事（但是，这比使用递归更好）。

Answer 2

final

你的代码就是它的冗余; while语句可以执行已经有递归调用的操作。 imo，while语句更好，因为递归通常会占用更多内存，但这只是一种观点。

你如何构建递归函数？

2 个答案: