Control flow python

Question

事实上，我已经习惯了c++，而且我被python卡住了。我似乎不明白是什么导致了while循环无限。该代码的主要目标是计算需要多少个月才能节省足够的预付款。

#*******Initializing all the required variables***********
home_price = float(input("Enter the price of your dream home:")) # cost of the home
down_payment_portion = 0.25 # initial upfront pay for the home which is 25%
stamp_duty_portion = 0.03 # 3%
annual_salary = float(input("Enter your annual salary:"))
tax_portion = 0.2 # 20%
save_amount = 0
save_portion = float(input("Enter the amount of money you want to save after tax-cut:"))
annual_return = 0.05 # 5%
months = 0
#*********************************************************
#------------Calculating all the necessary values---------
down_payment_portion = down_payment_portion * home_price # calculating the down payment for the dream home
stamp_duty_portion = stamp_duty_portion * home_price # calculating the stamp duty for the home
tax_portion = tax_portion * annual_salary # calculating the tax cut
save_portion = save_portion * save_amount # calculating the portion of tax-cut income to be put into savings
annual_return = (save_amount * annual_return) / 12
upfront_payment = down_payment_portion + stamp_duty_portion
while(save_amount < upfront_payment):
save_amount = save_amount + annual_return
save_amount = save_amount + (annual_salary - tax_portion) * save_portion / 12
months = months + 1
print(f'You will need {months} month to save enough for your upfront payment{upfront_payment}.')

Answer 1

1. 初始化save_amount = 0
2. 你得到annual_return作为annual_return = (save_amount * annual_return) / 12，它将是零
3. 您还得到save_portion作为save_portion = save_portion * save_amount，它再次为零
4. 因此，当循环从不递增时，中的save_amount也保持零，save_amount < upfront_payment始终为true==>无限循环

在您的代码中

while(save_amount < upfront_payment):
save_amount = save_amount + annual_return # 0 + 0 = 0
# 0 + (some value * 0)/12 = 0
save_amount = save_amount + (annual_salary - tax_portion) * save_portion / 12