爲什麼我無法隱式地將float轉換爲str？

Question

在運行時遇到了一些麻煩。基本上我只想得到一個金額，如果它超過50免費送貨，少於收取額外10美元。我繼續得到關於將float轉換爲str隱含的錯誤？我認爲我的意見應該被認爲是一個浮動？

#declare flags 
shippingCharge = 10 
freeShipping = False 
#Get number and convert to float? 
purchaseAmount = float(input("\nHow much is the purchase amount? ")) 

if (purchaseAmount) >= 50 : 
    freeShipping = True 
    print("Your purchase amount is " + purchaseAmount + "$ and shipping is free!") 
else : 
    print("Your purchase amount is " + purchaseAmount + "$ and shipping is " + shippingCharge + "$.") 
    purchaseAmount = shippingCharge + purchaseAmount 
    print("Your new total is " + purchaseAmount) 
print ("Have a nice day and thank you for shopping with us.") 

Answer 1

的問題是在你的打印語句：

print("Your purchase amount is " + purchaseAmount + "$ and shipping is free!") 

你是串聯字符串，無需轉換花車，嘗試添加一個STR（）轉換爲變量：

即：

print("Your purchase amount is " + str(purchaseAmount) + "$ and shipping is free!") 

你也可以我們Ë格式：

print("Your purchase amount is {0}$ and shipping is free!".format(purchaseAmount)) 

Answer 2

因爲Python是一個強類型語言：

https://wiki.python.org/moin/Why%20is%20Python%20a%20dynamic%20language%20and%20also%20a%20strongly%20typed%20language

您需要的類型顯式轉換爲字符串。它不會自動爲你自動執行。

Answer 3

只需使用str（purchaseAmount）替換purchaseAmount即可，您將會一切正常。

How much is the purchase amount? 50 
Your purchase amount is 50.0$ and shipping is free! 
Have a nice day and thank you for shopping with us. 

Answer 4

您輸入的是一個浮點數，因此它不能與字符串連接。你必須插入浮點數。

print('Your purchase amount is ${} and shipping is free!'.format(purchaseAmount))