如何在这段代码中添加输入？

Question

如果我使用下面的代码手动介绍参数，那么它将起作用：

def evaluatePoly(poly, x):
    result = 0
    for i in range(len(poly)):
        result += poly[i] * x ** i
    return float(result)

>>> evaluatePoly([1,2,2],2)
13

我想被要求仅介绍系数（不带括号）和要评估多项式方程的值。 像这样：

poly=(raw_input('Enter a list of coefficients from your polynomial equation: '))
x=int(raw_input('Enter the value where you want to evaluate your polynomial equation: '))

print(evaluatePoly(poly, x))

但是，如果我尝试这样做，Python会给我这个错误：

TypeError: unsupported operand type(s) for +=: 'int' and 'str'

我该怎么做？

谢谢

Answer 1

raw_input将返回一个字符串。 您可以将字符串处理为值列表，如下所示：

coeffs = raw_input('Enter a list of coefficients from your polynomial equation: ') # is a String
poly = coeffs.split() # split the string based on whitespace
poly = map(int, poly) # Convert each element to integer using int(...)

如果要接受浮点数，请使用float而不是int ；如果要分割逗号，请使用coeffs.split(",")而不是coeffs.split() 。

例

>>> x=int(raw_input('Enter the value where you want to evaluate your polynomial equation: '))
Enter the value where you want to evaluate your polynomial equation: 2
>>> coeffs = raw_input('Enter a list of coefficients from your polynomial equation: ')
Enter a list of coefficients from your polynomial equation: 3 2 5
>>> poly = coeffs.split()
>>> poly = map(int, poly)
>>> print(evaluatePoly(poly, x))
27.0
>>>

Answer 2

使用eval()评估您的input()列表，从字符串转换为列表。 您的评估可以在功能体内进行。 我是在这些行中这样做的

def evaluatePoly(poly, x):
    result = 0
    poly=eval(poly)
    for i in range(len(poly)):
        result += poly[i] * x ** i
    return float(result)

poly=(input('Enter a list of coefficients from your polynomial equation: '))
x=int(input('Enter the value where you want to evaluate your polynomial equation: '))

print(str(evaluatePoly(poly, x)))

我得到

>>> 
Enter a list of coefficients from your polynomial equation: [1,2]
Enter the value where you want to evaluate your polynomial equation: 5
11.0

请注意，使用eval()可能会对您的程序造成风险。