Python 如何从原始输入字符串值创建循环

我试图用我的程序来做的是要求用户输入一个输入字符串，该字符串稍后将使用str.upper或str.lower转换为大写或小写

我有5套选项供用户选择：

a = 'convert to upper case'
b =  'convert to lower case'
c = 'switch case of every alphabetic character to the opposite case'
d = 'convert first and last chrs of each word to upper case, and others to lower'
e = 'no change'

到目前为止，我已经完成了选项a和b的转换。但在我继续为选项c、d和e创建代码之前。我试图创建一个循环，但我不知道如何使用原始输入和字符串来创建循环

这是我目前掌握的代码：

# Conversion Rules

a = 'convert to upper case'
b =  'convert to lower case'
c = 'switch case of every alphabetic character to the opposite case'
d = 'convert first and last chrs of each word to upper case, and others to lower'
e = 'no change'


def upper(): 
    print 'Your Input: %s' % choice
    print 'Choosen Conversion Rule: %s' % a
    return 'Conversion Result: %s' % option_A

def lower(): 
    print 'Your Input: %s' % choice
    print 'Choosen Conversion Rule: %s' % b
    return 'Conversion Result: %s' % option_B


choice = str(raw_input('Choose an Option:'))    


if (choice == 'A') or (choice == 'a'): 
    value_A = str(raw_input('Enter a String to Convert:'))
    option_A = str.upper(Value_A) 
    print upper()

elif (choice == 'B') or ('b'): 
    value_B = str(raw_input('Enter a String to Convert:'))
    option_B = str.lower(value_B) 
    print lower()  

else:

    print 'Goodbye' # Here I want to break if 'Q' is entered if 'Q' is entered.

因此，在用户输入一个选项之后。例如“A”或“A”。第一个条件将运行，但是我想添加一个循环，返回到代码的开头，允许用户再次输入选项，或者选择一个不同的选项，以便运行不同的条件

choice = str(raw_input('Choose an Option:'))    


    if (choice == 'A') or (choice == 'a'): 
        value_A = str(raw_input('Enter a String to Convert:'))
        option_A = str.upper(Value_A) 
        print upper()

# I want to add a loop here to go back to the 'choice' variable.

---

您可以将所有用户界面放在一个while循环中，该循环将永远循环（例如，直到按下某个键）

请注意，“中断”是将您从循环中打断的部分。由于用户界面部分在while循环中，它将重复

# Conversion Rules
a = 'convert to upper case'
b =  'convert to lower case'
c = 'switch case of every alphabetic character to the opposite case'
d = 'convert first and last chrs of each word to upper case, and others to lower'
e = 'no change'

def upper(): 
    print 'Your Input: %s' % choice
    print 'Choosen Conversion Rule: %s' % a
    return 'Conversion Result: %s' % option_A

def lower(): 
    print 'Your Input: %s' % choice
    print 'Choosen Conversion Rule: %s' % b
    return 'Conversion Result: %s' % option_B

while True:
    choice = str(raw_input('Choose an Option:'))    

    if (choice == 'A') or (choice == 'a'): 
        value_A = str(raw_input('Enter a String to Convert:'))
        option_A = str.upper(Value_A) 
        print upper()
    elif (choice == 'B') or ('b'): 
        value_B = str(raw_input('Enter a String to Convert:'))
        option_B = str.lower(value_B) 
        print lower()  
    else:
        print 'Goodbye' # Here I want to break if 'Q' is entered if 'Q' is entered.
        break