How to make program go back to the top of the code instead of closing

Question

I m trying to figure out how to make Python go back to the top of the code  In SmallBasic  you do  start      textwindow writeline  Poo       goto start   But I can t figure out how you do that in Python    Any ideas anyone   The code I m trying to loop is this   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     So basically  when the user finishes their conversion  I want it to loop back to the top  I still can t put your loop examples into practise with this  as each time I use the def function to loop  it says that  op  is not defined

User · Answer

write a for or while loop and put all of your code inside of it  Goto type programming is a thing of the past    https   wiki python org moin ForLoop

User · Answer

You can easily do it with loops  there are two types of loops  For Loops   for i in range 0 5       print  Hello World    While Loops   count   1 while count  lt   5      print  Hello World      count    1   Each of these loops print  Hello World  five times

User · Answer

Use an infinite loop   while True      print  Hello world      This certainly can apply to your start   function as well  you can exit the loop with either break  or use return to exit the function altogether  which also terminates the loop   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      If you were to add an option to quit as well  that could be   if op lower   in   q    quit    e    exit        print  Goodbye        return   for example

User · Answer

Python has control flow statements instead of goto statements  One implementation of control flow is Python s while loop  You can give it a boolean condition  boolean values are either True or False in Python   and the loop will execute repeatedly until that condition becomes false  If you want to loop forever  all you have to do is start an infinite loop   Be careful if you decide to run the following example code  Press Control C in your shell while it is running if you ever want to kill the process  Note that the process must be in the foreground for this to work    while True        do stuff here     pass   The line   do stuff here is just a comment  It doesn t execute anything  pass is just a placeholder in python that basically says  Hi  I m a line of code  but skip me because I don t do anything    Now let s say you want to repeatedly ask the user for input forever and ever  and only exit the program if the user inputs the character  q  for quit   You could do something like this   while True      cmd   raw input  Do you want to quit  Enter   q          if cmd     q           break   cmd will just store whatever the user inputs  the user will be prompted to type something and hit enter   If cmd stores just the letter  q   the code will forcefully break out of its enclosing loop  The break statement lets you escape any kind of loop  Even an infinite one  It is extremely useful to learn if you ever want to program user applications which often run on infinite loops  If the user does not type exactly the letter  q   the user will just be prompted repeatedly and infinitely until the process is forcefully killed or the user decides that he s had enough of this annoying program and just wants to quit

User · Answer

You need to use a while loop  If you make a while loop  and there s no instruction after the loop  it ll become an infinite loop and won t stop until you manually stop it

User · Answer

Python  like most modern programming languages  does not support  goto   Instead  you must use control functions  There are essentially two ways to do this   1  Loops  An example of how you could do exactly what your SmallBasic example does is as follows   while True       print  Poo    It s that simple   2  Recursion  def the func        print  Poo     the func    the func     Note on Recursion  Only do this if you have a specific number of times you want to go back to the beginning  in which case add a case when the recursion should stop   It is a bad idea to do an infinite recursion like I define above  because you will eventually run out of memory   Edited to Answer Question More Specifically   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

User · Answer

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  gt   1 and key  lt   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  gt  ord  Z                        num -  26                 elif num  lt  ord  A                        num    26             elif symbol islower                    if num  gt  ord  z                        num -  26                 elif num  lt  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

[python] How to make program go back to the top of the code instead of closing

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