簡單的Python計算器

Question

嗨我是新來的蟒蛇，我正在練習通過一個簡單的計算器。 該方案可以讓我輸入數值爲一頓，稅和小費但這樣做的計算，當我得到這個錯誤：

Traceback (most recent call last): 
    File "C:/Users/chacha04231991/Desktop/pytuts/mealcost.py", line 5, in <module> 
    meal = meal + meal * tax 
TypeError: can't multiply sequence by non-int of type 'str' 

的是代碼：

meal = raw_input('Enter meal cost: ') 
tax = raw_input('Enter tax price in decimal #: ') 
tip = raw_input('Enter tip amount in decimal #: ') 

meal = meal + meal * tax 
meal = meal + meal * tip 

total = meal 
print 'your meal total is ', total 

Answer 1

你需要轉換你的輸入從字符串到數字，例如整數：

meal = int(raw_input('Enter meal cost: ')) 
tax = int(raw_input('Enter tax price in decimal #: ')) 
tip = int(raw_input('Enter tip amount in decimal #: ')) 

如果您需要輸入小數金額，也可以使用decimal類型。

from decimal import Decimal 
meal = Decimal(raw_input('Enter meal cost: ')) 
tax = Decimal(raw_input('Enter tax price in decimal #: ')) 
tip = Decimal(raw_input('Enter tip amount in decimal #: ')) 

我會建議你不要爲此使用浮點數，因爲它會給舍入誤差。

Answer 2

當您使用的raw_input，你得到的輸入型str

>>> meal = raw_input('Enter meal cost: ') 
Enter meal cost: 5 
>>> type(meal) 
<type 'str'> 

你應該執行行爲

>>> meal = int(raw_input('Enter meal cost: ')) 
Enter meal cost: 5 
>>> type(meal) 
<type 'int'> 

Answer 3

輸入之前將其轉換爲int/float是一個字符串，默認情況下，蟒蛇。在乘法之前，您必須將其轉換爲整數。

int(meal) 
int(tax) 
int(tip) 

應該這樣做。

Parse String to Float or Int