Python:如何打印此功能？

Question

#integers to be input
n = input('Enter \"n\" trials')
x = input('Enter \"x\" number of succeses')
p = input('Enter the probability \"p\" of success on a single trial')

#Probability Distribution function
def probDist(n, x, p):
    q = (1-p)**(n-x)
    numerator = math.factorial(n);
    denominator = math.factorial(x)* math.factorial(n-x);
    C = numerator / denominator;
    answer = C*p**x*q;

    return answer

# Does this have to come after I define the function? Or does this matter in Python
# Also this part just doesn't work.
dist = probDist(n, x, p);
print(dist);

这是我运行后得到的错误,我输入了所有的值.

Traceback (most recent call last):
   line 17, in <module>
    dist = probDist(n, x, p);
  line 9, in probDist
    q = (1-p)**(n-x)
TypeError: unsupported operand type(s) for -: 'int' and 'str'

Answer 1

在Python 3.x中,input 始终返回一个字符串,而不应用eval用户输入.Python 2.x input可以eval,但这很少是你想要的.如果你想要一个整数,请使用int(input(...))和如果你想要一个浮点数(与实数不完全相同,因为它只有有限的范围!),请使用float(input).(您应该抓住ValueError处理输入不合适的情况;如果这是用于锻炼/教育,那么现在可以暂时停止错误处理.)