python 2.7.3中的函數和參數

Question

在我的計算機科學課上，我剛剛開始學習 Python 中的函數和參數。 現在我的老師正在讓我們學習參數傳遞。 我沒有輸入我的程序的大量摘要，而是重新輸入下面的作業指南。

說明：在此程序中，用戶必須選擇輸入費用、輸入付款或顯示信用卡余額。 允許用戶通過在鍵盤上輸入代碼來表明他們的選擇。

使用以下函數名稱：

• enterValue 用戶輸入一個值

• addCharge 將傳遞給函數的值添加到余額中

• addPayment 從余額中減去傳遞給函數的值

• showBalance 顯示信用卡上的當前余額

讓用戶為適當的操作輸入以下代碼：

• “C”表示輸入費用

• “P”用於輸入付款

• “B”顯示余額

• 允許輸入交易，直到輸入“Z”

程序

balance = 0
def enterValue ():
    enter = input ("Enter a value.")
    return enter

def addCharge (enter,balance):
    balance = balance + enter
    return balance

def addPayment (enter,balance):
    balance = balance - enter
    return balance
def showBalance ():
    print "Your balance is... ", balance


transaction = raw_input ("Enter C for charges, P for payments, and B to show your balance. ") 
enterValue ()
while transaction != "Z":


    if transaction == "C":
        balance = addCharge(enter,balance)
        showBalance()        
    elif transaction == "P": 
        balance = addPayment (enter,balance)
        showBalance()
    elif transaction =="B":
        balance = enterValue()
        showBalance()
    transaction = raw_input ("Enter C for charges, P for payments, and B to show your balance. ") 

輸出

Enter C for charges, P for payments, and B to show your balance. P

Traceback (most recent call last):
  File "/Users/chrisblive/Downloads/Charge_Braverman-2.py", line 26, in <module>
    balance = addPayment (enter,balance)
NameError: name 'enter' is not defined

（我的問題是我在enterValue()值沒有被定義。）

Answer 1

練習的主要任務是了解將參數傳遞給函數。 所以只需將函數中所有需要的變量傳遞給它！ 大概你可以說所有函數都有自己的命名空間，如果你想在其中使用另一個級別的值，你必須將它作為參數傳遞，如果你想在較低級別重用它，則必須返回它。

例如：

###   Level "enterValue"   ###
def enterValue():
    return float(raw_input("Enter a value: "))
### End Level "enterValue" ###

###   Level "addCharge"   ###
def addCharge(enter, balance):
    balance = balance + enter
    return balance
### End Level "addCharge" ###

###   Level "showBalance"   ###
def showBalance(balance):
    print "Your balance is %f" % balance
### End Level "showBalance" ###

### Level "Mainlevel" ###
# This is where your program starts.
transaction = None
balance = 0.0
while transaction != "Z":
    transaction = raw_input("Enter C for charges, P for payments, and B to show your balance.\nEnter Z to exit: ").upper()

    if transaction == "C":
        enter = enterValue()
        balance = addCharge(enter, balance)
        showBalance(balance)
    elif transaction == "P":
        balance = addPayment(enter, balance)
        showBalance(balance)
    elif transaction == "B":
        showBalance(balance)
### End Level "Mainlevel" ###