我正在编写一个程序，允许用户从菜单中选择选项，并在此基础上打印所选选项的详细信息。我需要将数量和价格相乘才能得出成本。问题是，我的价格和数量都在嵌套词典中。如果用户选择选项1> 3AB，则应根据3AB的数量和价格打印出成本。我该怎么办？
stock = {
'3AB': {'Name': 'Telcom', 'Purchase Date': '12/12/2018', 'Price': '1.55', 'Volume':'3000'},
'S12': {'Name': 'S&P', 'Purchase Date': '12/08/2018', 'Price': '3.25', 'Volume': '2000'},
'AE1': {'Name': 'A ENG', 'Purchase Date': '04/03/2018', 'Price': '1.45', 'Volume': '5000'}
}
def menu():
menuChoice =True
while menuChoice:
print ("""
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
""")
menuChoice= input("Enter Choice: ")
if menuChoice=="1":
option1()
elif menuChoice=="2":
print("\n Buy Stock")
elif menuChoice=="3":
print("\n Sell Stock")
elif menuChoice=="4":
print("\n List Holdings")
elif menuChoice=="5":
print("\n List Sold Stock")
elif menuChoice=="0":
break
elif menuChoice !="":
print("\n Invalid. Please Re-enter choice: ")
def option1():
input1 = input("Please enter code: ").lower()
test = stock['3AB']['Volume'] * stock['3AB']['Price']
print(test)
if input1.upper() == "3AB":
print("\nCode: " + input1.upper())
print("Name: " + stock['3AB']['Name'])
print("Last Purchase Date: " + stock['3AB']['Purchase Date'])
print("Average Price: " + stock['3AB']['Price'])
print("Volume: " + stock['3AB']['Volume'])
print("Investment Cost ($): " + ())
elif input1.upper() == "S12":
print("\nCode: " + input1.upper())
print("Name: " + stock['S12']['Name'])
print("Last Purchase Date: " + stock['S12']['Purchase Date'])
print("Average Price: " + stock['S12']['Price'])
print("Volume: " + stock['S12']['Volume'])
elif input1.upper() == "AE1":
print("\nCode: " + input1.upper())
print("Name: " + stock['AE1']['Name'])
print("Last Purchase Date: " + stock['AE1']['Purchase Date'])
print("Average Price: " + stock['AE1']['Price'])
print("Volume: " + stock['AE1']['Volume'])
else:
print("Stock is not found in your portfolio.")
print(input("Enter another option: "))
menu()
答案 0 :(得分：0)
问题是您将值作为字符串存储在原始字典中。要解决此问题，您只需将值转换为float即可：
test = float(stock['3AB']['Volume']) * float(stock['3AB']['Price'])
或者不要更改代码并将值存储为数字：
stock = {
'3AB': {'Name': 'Telcom', 'Purchase Date': '12/12/2018', 'Price': 1.55, 'Volume':3000},
'S12': {'Name': 'S&P', 'Purchase Date': '12/08/2018', 'Price': 3.25, 'Volume': 2000},
'AE1': {'Name': 'A ENG', 'Purchase Date': '04/03/2018', 'Price': 1.45, 'Volume': 5000}
}
顺便说一句，在下面的代码中，您的代码仍然存在一个问题。您必须定义一个要打印的值：
print("Investment Cost ($): " + ())
答案 1 :(得分：0)
您需要在字典中输入数字-而不是字符串。您还可以通过使用字典而不是大型的if-elif-construct来调用函数来使代码“更灵活”。使用函数来请求数字/输入也是减少重复编码的好方法（DRY-不要重复自己）：
在字典中固定数字（或直接使用数字）：
stock = {
'3AB': {'Name': 'Telcom', 'Purchase Date': '12/12/2018',
'Price': float('1.55'), 'Volume': int('3000')},
'S12': {'Name': 'S&P', 'Purchase Date': '12/08/2018',
'Price': float('3.25'), 'Volume': int('2000')},
'AE1': {'Name': 'A ENG', 'Purchase Date': '04/03/2018',
'Price': float('1.45'), 'Volume': int('5000')} }
不要重复自己：
def inputNumber(text,r):
"""Handles numeric input - input must be inside r (f.e. a range/set/list)."""
while True:
try:
choice = int(input(text))
if choice in r:
return choice
except ValueError:
print("Wrong choice - try again.")
def inputTextUpper(r):
"""Handles text input - text must be inside r (a list/set/...) and is returned as
upper(). If nothing is inputted the function returns None."""
while True:
try:
choice = input("Choose one: {} - return to skip.".format(str(r))).upper()
if choice in r:
return choice
elif not choice:
return None # empty input
except ValueError:
print("Wrong choice - try again.")
映射函数以输入并调用它们：
def buy():
input1 = inputTextUpper([x for x in stock.keys()])
what = stock.get(input1) # get the inner dict or None if empty input
if not what:
print("Back to main menue")
return
# using , instead of + to avoid errors when print numbers - you should probably
# read about str.format() or f""-strings to make formatting "better"
print("\nCode: ", input1)
print("Name: ", what['Name'])
print("Last Purchase Date: ", what['Purchase Date'])
print("Average Price: ", what['Price'])
print("Volume: ", what['Volume'])
print("Investment Cost ($): ", what['Volume']*what['Price'])
def dummy():
print("Not implemented")
def menu():
# map an input to a function call (the name of the function to be called)
funcMapp = {1:buy, 2:dummy, 3:dummy, 4:dummy,5:dummy} # lots of dummies
while True:
menuChoice = inputNumber("""
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
""", range(6))
if menuChoice == 0:
break
# execute the function choosen
funcMapp[menuChoice] () # this gets the function from the dict and calls it
menu()
一次运行的输出：
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
Dunno
Wrong choice - try again.
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
2
Not implemented
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
1
Choose one: ['3AB', 'S12', 'AE1'] - return to skip.None
Choose one: ['3AB', 'S12', 'AE1'] - return to skip.asdf
Choose one: ['3AB', 'S12', 'AE1'] - return to skip.3ab
Code: 3AB
Name: Telcom
Last Purchase Date: 12/12/2018
Average Price: 1.55
Volume: 3000
Investment Cost ($): 4650.0
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
1
Choose one: ['3AB', 'S12', 'AE1'] - return to skip.
Back to main menue
Menu
1. List Holding and Sold details for a Stock
2. Buy Stock
3. Sell Stock
4. list Holdings
5. list Sold Stock
0. Exit
0
有关如何避免KeyError的问题，请参见Why dict.get(key) instead of dict[key]?，有关更多格式化选项的信息，请参见string formating。