如何存储和使用数学运算符作为python变量

How to store and use mathematical operators as python variable

我对python不太熟悉，尝试在下面编写类似的代码(代码A)，因此它与代码B非常相似。我想使用用户输入的数学运算符作为do_what变量。我们如何用python编写这段代码(a)，使其像代码b一样工作？

代码A

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num1 = input("Enter a number:")
num2 = input("Enter another number:")
do_what = input("Enter a calculation symbol for calculation you want to perform:")
result = float(num1) do_what float(num2)
print("result is:" + str(result))

代码B

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num1 = input("Enter a number:")
num2 = input("Enter another number:")
result = int(num1) + int(num2)
print("result is:" + str(result))

相关讨论

您可以将运算符模块用于常用运算符，并创建查找字典以将符号映射到函数。如果您不希望操作员出现在该模块中，您可以简单地定义自定义函数，并以相同的方式添加查找它们：

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import operator

operatorlookup = {
'+': operator.add,
'-': operator.sub,
'*': operator.mul,
'/': operator.truediv
}

num1 = input("Enter a number:")
num2 = input("Enter another number:")
do_what = input("Enter calculation symbols for calculation you want to perform:")

op = operatorlookup.get(do_what)

if op is not None:
result = op(float(num1), float(num2))
else:
result ="Unknown operator"
print("result is:" + str(result))

您可能还对了解内置函数eval感兴趣。这会将if和else循环减少为针对您的这个特定示例的单个语句

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num1 = input("Enter a number:")
num2 = input("Enter another number:")
do_what = input("Enter calculation symbols for calculation you want to perform:")

result = eval(num1 + do_what + num2)
print("result is: %s" %result)

# Enter a number: 3
# Enter another number: 18
# Enter calculation symbols for calculation you want to perform: *
# result is: 54

编辑

在这种情况下，为了使eval稍微安全一些，您可以使用类似的东西

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if do_what in ['+', '-', '*', '**', '/']:
result = eval(num1 + do_what + num2)
print("result is: %s" %result)
else:
print ("Enter an arithmetic operator")