python - 由于 for 循环，打印功能失败

Question

当我注释掉 for 循环时，一切正常。但是，一旦它再次处于活动状态，IDLE 就会吐出​​一个语法错误。我已经尝试适当地间隔它，因为这是对其他问题的建议之一，但无论我输入多少次，这都没有奏效。

# futval.py
# A program to compute the value of an investment
# carried 10 years into the future

#begins main function of program

def main():

    #description of program 

    print("This program calculates the future value")
    print("of a 10-year investment.")

    #creates and assign three variables to user input

    principal = eval(input("Enter the initial principal: "))
    apr = eval(input("Enter the annual interest rate: "))
    compound = eval(input("How often is the interest compounded: "))

    #begins a 'for' loop that iterates 10 times indicative of 10 years

    for i in range(10):
        print (principal)
        principal = principal * (1 + (apr/compound)

    #prints out the final result of the above equation. 
    print("The value in 10 years is:",principal)

    #original program exited too fast and didn't allow user to see output
    #I added the following line so the user could see.

    print(input("Press enter to exit."))

main()

标签： pythonfor-loopprinting

Answer 1

语法错误是您缺少一个右括号：更改principal = principal * (1 + (apr/compound) 为principal = principal * (1 + (apr/compound))

此外，你应该改掉使用的习惯，eval因为它通常被认为是危险的，在这里绝对不需要。只需转换为类型并捕获异常就可以了。