Question

我正在学习Python中的函数，并被要求创建一个脚本，该脚本需要两个输入值，并对它们执行一些数学运算。我编写了下面的代码，但不断收到错误消息，在第17行，我尝试打印答案，'结果'没有定义。我不明白这一点，因为我觉得我在每个函数中定义'结果'。显然，我遗漏了一些与函数和返回值相关的基本概念。任何帮助将不胜感激。

def sum(a,b):
    result = a + b
    return result

def times(a,b):
    result = a * b
    return result

def divide(a,b):
    result = a / b
    return result

def subtract(a,b):
    result = a / b
    return result

print "Answer is %d" % result

def start():
    print "This program can perfom a math function of any two numbers"
    a = int(raw_input("Enter first number: "))
    b = int(raw_input("Enter second number: "))
    c = raw_input("Enter math function you want: ")

    if c == "+":
        sum(a,b)
    elif c == "x":
        times(a,b)
    elif c == "/":
        divide(a,b)
    elif c == "-":
        subtract(a,b)
    else:
        print "you didnt enter a function!"

start()

这是错误：文件“defPrac2.py”，第17行，in 打印“答案是％d”％结果

Answer 1

看到问题是你没有从启动功能返回任何东西，再次Python遵循缩进级别，即在第一级写入的任何内容（没有空格的行将首先执行），

从顶部删除行打印行并修改start函数以返回值：

def start():
    print "This program can perfom a math function of any two numbers"
    a = int(raw_input("Enter first number: "))
    b = int(raw_input("Enter second number: "))
    c = raw_input("Enter math function you want: ")
    res = -1
    if c == "+":
        res = sum(a,b)
    elif c == "x":
        res = times(a,b)
    elif c == "/":
        res = divide(a,b)
    elif c == "-":
        res = subtract(a,b)
    else:
        print "you didnt enter a function!"
    return res
result = start()
# use format instead of access specifier as it may give you error if 
# not handling the specific type case format is more generic
print "Answer is {0}".format(result)

快乐编码：）

Answer 2

尝试此操作，当您有返回值时，您可以将该值放入新变量中，然后在print语句中打印或直接打印。 `

def sum(a,b):
    result = a + b
    return result

def times(a,b):
    result = a * b
    return result

def divide(a,b):
    result = a / b
    return result

def subtract(a,b):
    result = a / b
    return result

def start():
    print "This program can perfom a math function of any two numbers"
    a = int(raw_input("Enter first number: "))
    b = int(raw_input("Enter second number: "))
    c = raw_input("Enter math function you want: ")

    if c == "+":
        print("The answer is "+sum(a,b))
    elif c == "x":
        print("The answer is "+times(a,b))
    elif c == "/":
        print("The answer is "+divide(a,b))
    elif c == "-":
        print("The answer is "+subtract(a,b))
    else:
        print "you didnt enter a function!"

start()

`

如何在Python中打印返回的值

2 个答案: