我正在试图弄清楚如何让Python回到代码的顶端。在SmallBasic中,你做
start:
textwindow.writeline("Poo")
goto start
但是我无法弄清楚你是如何用Python做的:/任何人的想法?
我试图循环的代码就是这个
#Alan's Toolkit for conversions
def start() :
print ("Welcome to the converter toolkit made by Alan.")
op = input ("Please input what operation you wish to perform. 1 for Fahrenheit to Celsius, 2 for meters to centimetres and 3 for megabytes to gigabytes")
if op == "1":
f1 = input ("Please enter your fahrenheit temperature: ")
f1 = int(f1)
a1 = (f1 - 32) / 1.8
a1 = str(a1)
print (a1+" celsius")
elif op == "2":
m1 = input ("Please input your the amount of meters you wish to convert: ")
m1 = int(m1)
m2 = (m1 * 100)
m2 = str(m2)
print (m2+" m")
if op == "3":
mb1 = input ("Please input the amount of megabytes you want to convert")
mb1 = int(mb1)
mb2 = (mb1 / 1024)
mb3 = (mb2 / 1024)
mb3 = str(mb3)
print (mb3+" GB")
else:
print ("Sorry, that was an invalid command!")
start()
基本上,当用户完成转换时,我希望它循环回到顶部。我仍然无法将循环示例付诸实践,因为每次我使用def函数循环时,都会说“op”没有定义。
答案 0 :(得分:16)
使用无限循环:
while True:
print('Hello world!')
这当然也适用于您的start()
功能;您可以使用break
退出循环,或使用return
完全退出该函数,这也会终止循环:
def start():
print ("Welcome to the converter toolkit made by Alan.")
while True:
op = input ("Please input what operation you wish to perform. 1 for Fahrenheit to Celsius, 2 for meters to centimetres and 3 for megabytes to gigabytes")
if op == "1":
f1 = input ("Please enter your fahrenheit temperature: ")
f1 = int(f1)
a1 = (f1 - 32) / 1.8
a1 = str(a1)
print (a1+" celsius")
elif op == "2":
m1 = input ("Please input your the amount of meters you wish to convert: ")
m1 = int(m1)
m2 = (m1 * 100)
m2 = str(m2)
print (m2+" m")
if op == "3":
mb1 = input ("Please input the amount of megabytes you want to convert")
mb1 = int(mb1)
mb2 = (mb1 / 1024)
mb3 = (mb2 / 1024)
mb3 = str(mb3)
print (mb3+" GB")
else:
print ("Sorry, that was an invalid command!")
如果你要添加一个退出选项,那可能是:
if op.lower() in {'q', 'quit', 'e', 'exit'}:
print("Goodbye!")
return
例如。
答案 1 :(得分:5)
<强> 1。环强>
如何完全按照SmallBasic示例执行操作的示例如下:
while True :
print "Poo"
就这么简单。
<强> 2。递归强>
def the_func() :
print "Poo"
the_func()
the_func()
关于递归的注意事项:只有在您想要返回到开头的特定次数时才执行此操作(在这种情况下,在递归应该停止时添加一个案例)。像我上面定义的那样进行无限递归是一个坏主意,因为你最终会耗尽内存!
#Alan's Toolkit for conversions
invalid_input = True
def start() :
print ("Welcome to the converter toolkit made by Alan.")
op = input ("Please input what operation you wish to perform. 1 for Fahrenheit to Celsius, 2 for meters to centimetres and 3 for megabytes to gigabytes")
if op == "1":
#stuff
invalid_input = False # Set to False because input was valid
elif op == "2":
#stuff
invalid_input = False # Set to False because input was valid
elif op == "3": # you still have this as "if"; I would recommend keeping it as elif
#stuff
invalid_input = False # Set to False because input was valid
else:
print ("Sorry, that was an invalid command!")
while invalid_input : # this will loop until invalid_input is set to be True
start()
答案 2 :(得分:2)
Python具有控制流语句而不是goto
语句。控制流的一个实现是Python的while
循环。您可以给它一个布尔条件(在Python中布尔值为True或False),并且循环将重复执行,直到该条件变为false。如果你想永远循环,你所要做的就是开始一个无限循环。
如果您决定运行以下示例代码,请务必小心。如果您想杀死进程,请在shell运行时按下Control + C.请注意,该过程必须位于前台才能使其正常工作。
while True:
# do stuff here
pass
行# do stuff here
只是一个评论。它不会执行任何操作。 pass
只是python中的占位符,基本上说“嗨,我是一行代码,但跳过我因为我什么也没做。”
现在让我们假设您要反复询问用户输入永远,并且只有在用户输入字符'q'退出时才退出程序。
你可以这样做:
while True:
cmd = raw_input('Do you want to quit? Enter \'q\'!')
if cmd == 'q':
break
cmd
将存储用户输入的任何内容(系统会提示用户键入内容并按Enter键)。如果cmd
只存储字母'q',则代码将强制break
退出其封闭循环。 break
语句允许您转义任何类型的循环。即使是无限的!如果您想要编写通常在无限循环上运行的用户应用程序,那么了解它非常有用。如果用户没有完全输入字母'q',则会反复无限地提示用户,直到该过程被强制终止,或者用户认为他已经有足够的烦人程序并且只想退出。
答案 3 :(得分:2)
您可以使用循环轻松完成,有两种类型的循环
对于循环:
for i in range(0,5):
print 'Hello World'
虽然循环:
count = 1
while count <= 5:
print 'Hello World'
count += 1
这些循环中的每一个都打印“Hello World”五次
答案 4 :(得分:0)
编写for或while循环并将所有代码放入其中?转到类型编程已成为过去。
答案 5 :(得分:0)
您需要使用while循环。如果你做了一个while循环,并且在循环之后没有指令,它将变成一个无限循环,并且在你手动停止它之前不会停止。
答案 6 :(得分:0)
def start():
Offset = 5
def getMode():
while True:
print('Do you wish to encrypt or decrypt a message?')
mode = input().lower()
if mode in 'encrypt e decrypt d'.split():
return mode
else:
print('Please be sensible try just the lower case')
def getMessage():
print('Enter your message wanted to :')
return input()
def getKey():
key = 0
while True:
print('Enter the key number (1-%s)' % (Offset))
key = int(input())
if (key >= 1 and key <= Offset):
return key
def getTranslatedMessage(mode, message, key):
if mode[0] == 'd':
key = -key
translated = ''
for symbol in message:
if symbol.isalpha():
num = ord(symbol)
num += key
if symbol.isupper():
if num > ord('Z'):
num -= 26
elif num < ord('A'):
num += 26
elif symbol.islower():
if num > ord('z'):
num -= 26
elif num < ord('a'):
num += 26
translated += chr(num)
else:
translated += symbol
return translated
mode = getMode()
message = getMessage()
key = getKey()
print('Your translated text is:')
print(getTranslatedMessage(mode, message, key))
if op.lower() in {'q', 'quit', 'e', 'exit'}:
print("Goodbye!")
return