How to Emulate a Do-While Loop

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

how to emulate the do while statement in python?

Python doesn't have a do while loop, u can simulate it like this

i = 1  

while True:  
    print(i)  
    i = i + 1  
    if(i > 100):  
        break  

Emulating a do-while loop in Bash

Two simple solutions:

1. Execute your code once before the while loop

   actions() {
      check_if_file_present
      # Do other stuff
   }
   
   actions #1st execution
   while [ current_time <= $cutoff ]; do
      actions # Loop execution
   done
   

2. Or:

   while : ; do
       actions
       [[ current_time <= $cutoff ]] || break
   done
   

Why there is no do while loop in python

There is no do...while loop because there is no nice way to define one that fits in the statement: indented block pattern used by every other Python compound statement. As such proposals to add such syntax have never reached agreement.

Nor is there really any need to have such a construct, not when you can just do:

while True:
    # statement(s)
    if not condition:
        break

and have the exact same effect as a C do { .. } while condition loop.

See PEP 315 -- Enhanced While Loop:

Rejected [...] because no syntax emerged that could
compete with the following form:

    while True:
        <setup code>
        if not <condition>:
            break
        <loop body>

A syntax alternative to the one proposed in the PEP was found for
a basic do-while loop but it gained little support because the
condition was at the top:

    do ... while <cond>:
        <loop body>

or, as Guido van Rossum put it:

Please reject the PEP. More variations along these lines won't make the
language more elegant or easier to learn. They'd just save a few hasty
folks some typing while making others who have to read/maintain their code
wonder what it means.

Why is my nested while loop not working? if and second while loop is expected

Try this

used = []

#First Loop
while True:
    search = True #moved search = True here so that the nested loop will run each iteration of the main loop as it will be set back to True
    pic = driver.find_element(By.CSS_SELECTOR,value=".image-post img")
    time.sleep(2)
    pic_url = pic.get_attribute("src") #you’re not doing anything with this from the looks of it
    pic_title = pic.get_attribute("alt") #same with this
    used.append(pic)
    time.sleep(200)

#Second loop
        while search:
            pic = driver.find_element(By.CSS_SELECTOR, value=".image-post img")
            if pic != used:#may want to change “used” to “used[-1]” here as used is a list while it appears pic is not, so the -1 will get the last value in used
                search = False

    used.append(pic)

You could also replace search with True and change the “search = False” with “break”

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