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stackoverflow.com › questions › 743164 › how-to-emulate-a-do-while-loop

I am not sure what you are trying to do. You can implement a do-while loop like this:

while True:
  stuff()
  if fail_condition:
    break

Or:

stuff()
while not fail_condition:
  stuff()

What are you doing trying to use a do while loop to print the stuff in the list? Why not just use:

for i in l:
  print i
print "done"

Update:

So do you have a list of lines? And you want to keep iterating through it? How about:

for s in l: 
  while True: 
    stuff() 
    # use a "break" instead of s = i.next()

Does that seem like something close to what you would want? With your code example, it would be:

for s in some_list:
  while True:
    if state is STATE_CODE:
      if "//" in s:
        tokens.add( TOKEN_COMMENT, s.split( "//" )[1] )
        state = STATE_COMMENT
      else :
        tokens.add( TOKEN_CODE, s )
    if state is STATE_COMMENT:
      if "//" in s:
        tokens.append( TOKEN_COMMENT, s.split( "//" )[1] )
        break # get next s
      else:
        state = STATE_CODE
        # re-evaluate same line
        # continues automatically

Answer from Tom on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 743164 › how-to-emulate-a-do-while-loop

python - How to emulate a do-while loop? - Stack Overflow

Top answer

1 of 16

1331

I am not sure what you are trying to do. You can implement a do-while loop like this:

while True:
  stuff()
  if fail_condition:
    break

Or:

stuff()
while not fail_condition:
  stuff()

What are you doing trying to use a do while loop to print the stuff in the list? Why not just use:

for i in l:
  print i
print "done"

Update:

So do you have a list of lines? And you want to keep iterating through it? How about:

for s in l: 
  while True: 
    stuff() 
    # use a "break" instead of s = i.next()

Does that seem like something close to what you would want? With your code example, it would be:

for s in some_list:
  while True:
    if state is STATE_CODE:
      if "//" in s:
        tokens.add( TOKEN_COMMENT, s.split( "//" )[1] )
        state = STATE_COMMENT
      else :
        tokens.add( TOKEN_CODE, s )
    if state is STATE_COMMENT:
      if "//" in s:
        tokens.append( TOKEN_COMMENT, s.split( "//" )[1] )
        break # get next s
      else:
        state = STATE_CODE
        # re-evaluate same line
        # continues automatically

2 of 16

413

Here's a very simple way to emulate a do-while loop:

condition = True
while condition:
    # loop body here
    condition = test_loop_condition()
# end of loop

The key features of a do-while loop are that the loop body always executes at least once, and that the condition is evaluated at the bottom of the loop body. The control structure show here accomplishes both of these with no need for exceptions or break statements. It does introduce one extra Boolean variable.

DataCamp

datacamp.com › tutorial › do-while-loop-python

Emulating a Do-While Loop in Python: A Comprehensive Guide for Beginners | DataCamp

January 31, 2024 - Python does not have a built-in "do-while" loop, but you can emulate its behavior.

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Why do you choose Python over other language?

A few off the top of my head:

Huge standard library
Generally good quality documentation for standard library
Gobs of third-party modules to rival even Java
Platform agnostic, and present in virtually every *nix distribution I'm aware of without even needing to install it (because so many system tools are written using it)
Very common use of BSD/MIT-style licencing with third-party modules; GPL licencing gives corporate lawyers a big headache
Emphasis on code readability (see PEP-8) and DRY principles without sacrificing readability (kind of a middle ground between perl and java, I guess?)
Useful for a really broad range of programming tasks from little shell scripts to enterprise web applications to scientific uses; it may not be as good at any of those as a purpose-built programming language but it can do all of them, and do them well (e.g. you don't see web apps written as bash scripts nor do you see linux package managers written in Java)

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