Question

我对Python很新，我只是想知道最好的方法是什么（非常简单的问题）：

我有一个提示用户选择选项的功能，如果他们输入的选项无效，它将再次调用该功能：

def choose_colour():
    print "Select colour:"
    print "1. Red"
    print "2. Blue"
    print "3. Green"
    selection = raw_input()

最初我有一个if语句比较输入和IF它是一个不正确的输入我会再次调用该函数本身。这是不实际和错误的。

def choose_colour():
    print "Select colour:"
    print "1. Red"
    print "2. Blue"
    print "3. Green"
    selection = raw_input()

    if selection == "1":
         colour = "Red"
    elif selection == "2":
         colour = "Blue"
    elif selection == "3":
         colour = "Green"
    else:
         print "Please select, 1, 2 or 3"
         choose_colour()

编辑：

这有效，但我更喜欢循环解决方案。

def set_TPL_colour():
    print "Enter TPL colour value:"
    print "1. WHITE"
    print "2. GREEN"
    print "3. AMBER"
    print "4. RED"
    print ">>>",
    option = raw_input()
    if option == "1":
        tpl_colour = "WHITE"
        return tpl_colour
    elif option == "2":
        tpl_colour = "GREEN"
        return tpl_colour
    elif option == "3":
        tpl_colour = "AMBER"
        return tpl_colour
    elif option == "4":
        tpl_colour = "RED"
        return tpl_colour
    else:
        print "ERROR incorrect option selection"
        tpl_colour = set_TPL_colour()
        return tpl_colour

Answer 1

您不需要再次调用该函数，只需将其置于while循环中并在输入无效时重新分配该变量：

def choose_colour():
    print "Select colour:"
    print "1. Red"
    print "2. Blue"
    print "3. Green"
    selection = raw_input()
    while selection not in ("1","2","3"):
        print "Please choose a valid option"
        selection = raw_input()
    if selection == "1":
        colour = "Red"
    elif selection == "2":
        colour = "Blue"
    elif selection == "3":
        colour = "Green"

清洁版：

def choose_colour():
    colourChoices = {"1":"Red", "2":"Blue", "3":"Green"}
    selection = raw_input("Select colour:\n 1. Red\n 2. Blue\n 3. Green")
    while !colourChoices[selection]:
        print "Please enter valid data"
        selection = raw_input("Select colour:\n 1. Red\n 2. Blue\n 3. Green")
    colour = colourChoices[selection]

Answer 2

使用字典，示例 -

def choose_colour():
    print "Select colour:"
    print "1. Red"
    print "2. Blue"
    print "3. Green"
    colordict = {"1":"Red" , "2":"Blue", "3":"Green"}
    selection = raw_input()
    ret = colordict.get(selection)
    if not ret:
        return choose_colour()
    return ret

你也可以做while循环 -

def choose_colour():
    colordict = {"1":"Red" , "2":"Blue", "3":"Green"}
    ret = None
    while not ret:
        print "Select colour:"
        print "1. Red"
        print "2. Blue"
        print "3. Green"
        selection = raw_input()
        ret = colordict.get(selection)
    return ret

示例/演示 -

>>> def choose_colour():
...     print "Select colour:"
...     print "1. Red"
...     print "2. Blue"
...     print "3. Green"
...     colordict = {"1":"Red" , "2":"Blue", "3":"Green"}
...     selection = raw_input()
...     ret = colordict.get(selection)
...     if not ret:
...         return choose_colour()
...     return ret
...
>>> choose_colour()
Select colour:
1. Red
2. Blue
3. Green
5
Select colour:
1. Red
2. Blue
3. Green
2
'Blue'

Answer 3

像这样。

input = raw_input()
while not_valid(input):
   print_options()
   input = raw_input()

Answer 4

您可以使用简单的方法。首先，使用我的Input（）函数和控制错误。此外，你可以在这里放一个长长的列表，这个程序可以处理它。

# If your input value is only a number then use "Value.isdigit() == False".
# If you need an input that is a text, you should remove "Value.isdigit() == False".
def Input(Message):
    Value = None
    while Value == None or Value.isdigit() == False:
        try:        
            Value = str(input(Message)).strip()
        except InputError:
            Value = None
    return Value

# Your answer:
def choose_colour():
    # Your colors list
    Colors = ["Red", "Blue", "Green"]
    # Print your menu
    print("Select colour:")        
    for Item in Colors:
        print(str(Colors.index(Item) + 1) + ". " + Item)
    print("")
    Choice = -1
    # If user entered an incorrect answer, ask your question again
    while Choice <=0 or Choice > len(Colors):
        Choice = int(Input("Your choice: "))
    # Print user choice
    print("You choosed " + Colors[Choice - 1])

choose_colour()

如果输入不正确，Python再次调用函数

4 个答案: