What does while True mean in Python

Question

def play game word list       hand   deal hand HAND SIZE    random init     while True          cmd   raw input  Enter n to deal a new hand  r to replay the last hand  or e to end game             if cmd     n               hand   deal hand HAND SIZE              play hand hand copy    word list              print         elif cmd     r               play hand hand copy    word list              print         elif cmd     e               break         else              print  Invalid command     While WHAT is True   I reckon saying  while true  is shorthand  but for what  While the variable  hand  is being assigned a value  And what if the variable  hand  is not being assigned a value

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while True mean infinite loop  this usually use by long process  you can change   while True    with  while 1

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To answer your question directly  while the loop condition is True   Which it always is  in this particular bit of code

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In this context  I suppose it could be interpreted as   do     while cmd      e

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while True is true -- ie always   This is an infinite loop  Note the important distinction here between True which is a keyword in the language denoting a constant value of a particular type  and  true  which is a mathematical concept

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while loops continue to loop until the condition is false  For instance  pseudocode    i   0 while i  lt  10   i     With each iteration of the loop  i will be incremented by 1  until it is 10  At that point  the condition i  lt  10 is no longer true  and the loop will complete   Since the condition in while True is explicitly and always true  the loop will never end  until it is broken out of some other way  usually by a construct like break within the loop body

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A while loop takes a conditional argument  meaning something that is generally either true or false  or can be interpreted as such   and only executes while the condition yields True   As for while True  Well  the simplest true conditional is True itself  So this is an infinite loop  usually good in a game that requires lots of looping   More common from my perspective  though  is to set some sort of  done  variable to false and then making that true to end the game  and the loop would look more like while not done  or whatever

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Formally  True is a Python built-in constant of bool type    You can use Boolean operations on bool types  at the interactive python prompt for example  and convert numbers into bool types    gt  gt  gt  print not True False  gt  gt  gt  print not False True  gt  gt  gt  print True or False True  gt  gt  gt  print True and False False  gt  gt  gt  a bool 9   gt  gt  gt  print a True  gt  gt  gt  b bool 0   gt  gt  gt  print b False  gt  gt  gt  b bool 0 000000000000000000000000000000000001   gt  gt  gt  print b True   And there are  gotcha s  potentially with what you see and what the Python compiler sees    gt  gt  gt  n 0  gt  gt  gt  print bool n  False  gt  gt  gt  n  0   gt  gt  gt  print bool n  True  gt  gt  gt  n 0 0  gt  gt  gt  print bool n  False  gt  gt  gt  n  0 0   gt  gt  gt  print bool n  True   As a hint of how Python stores bool types internally  you can cast bool types to integers and True will come out to be 1 and False 0    gt  gt  gt  print True 0 1  gt  gt  gt  print True 1 2  gt  gt  gt  print False 0 0  gt  gt  gt  print False 1 1   In fact  Python bool type is a subclass of Python s int type    gt  gt  gt  type True   lt type  bool  gt   gt  gt  gt  isinstance True  int  True   The more important part of your question is  What is while True   is  what is True   and an important corollary  What is false    First  for every language you are learning  learn what the language considers  truthy  and  falsey   Python considers Truth slightly differently than Perl Truth for example  Other languages have slightly different concepts of true   false  Know what your language considers to be True and False for different operations and flow control to avoid many headaches later   There are many algorithms where you want to process something until you find what you are looking for  Hence the infinite loop or indefinite loop  Each language tend to have its own idiom for these constructs  Here are common C infinite loops  which also work for Perl   for          loop until break          or     while  1       return if  function arg   gt  3       The while True  form is common in Python for indefinite loops with some way of breaking out of the loop  Learn Python flow control to understand how you break out of while True loops  Unlike most languages  for example  Python can have an else clause on a loop  There is an example in the last link

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my question  while WHAT is True    Everything inside the    of the while statement is going to be evaluated as a boolean  Meaning it gets converted into either true or false   Consider in the statement while 6  gt  5    It first evaluates the expression 6  gt  5 which is true so is the same as saying while true   Anything that is not FALSE  0  an emptry string     null  or undefined is likely to be evaluated to true   When I first started programming I used to do things like if foo    true   I didn t realise that was virtually the same thing as if foo     So when you say while true  its like are saying while true    true   So to answer you question  While TRUE is True

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my question  while WHAT is True    While True is True   The while loop will run as long as the conditional expression evaluates to True   Since True always evaluates to True  the loop will run indefinitely  until something within the loop returns or breaks

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While most of these answers are correct to varying degrees  none of them are as succinct as I would like  Put simply  using while True  is just a way of running a loop that will continue to run until you explicitly break out of it using break or return   Since True will always evaluate to True  you have to force the loop to end when you want it to  while True        do stuff      if some condition          break        do more stuff - code here WILL NOT execute when  if some condition   evaluates to True  While normally a loop would be set to run until the while condition is false  or it reaches a predefined end point  do next   True  while do next         do stuff      if some condition          do next   False        do more stuff - code here WILL execute even when  if some condition   evaluates to True  Those two code chunks effectively do the same thing If the condition your loop evaluates against is possibly a value not directly in your control  such as a user input value  then validating the data and explicitly breaking out of the loop is usually necessary  so you d want to do it with either method  The while True format is more pythonic since you know that break is breaking the loop at that exact point  whereas do next   False could do more stuff before the next evaluation of do next

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True is always True  so while True will loop forever   The while keyword takes an expression  and loops while the expression is true  True is an expression that is always true   As a possibly clarifying example  consider the following   a   1 result   a    1   Here  a    1 will return True  and hence put True into result  Hence    a   1 while a    1          is equivalent to   while True          provided you don t alter the value of a inside the while loop

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Nothing evaluates to True faster than True  So  it is good if you use while True instead of while 1  1 etc

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while True            means infinite loop   The while statement is often used of a finite loop  But using the constant  True  guarantees the repetition of the while statement without the need to control the loop  setting a boolean value inside the iteration for example   unless you want to break it   In fact  True     1    1

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while True means loop forever  The while statement takes an expression and executes the loop body while the expression evaluates to  boolean   true   True always evaluates to boolean  true  and thus executes the loop body indefinitely  It s an idiom that you ll just get used to eventually  Most languages you re likely to encounter have equivalent idioms   Note that most languages usually have some mechanism for breaking out of the loop early  In the case of Python it s the break statement in the cmd     e  case of the sample in your question

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Anything can be taken as True until the opposite is presented  This is the way duality works  It is a way that opposites are compared  Black can be True until white at which point it is False  Black can also be False until white at which point it is True  It is not a state but a comparison of opposite states  If either is True the other is wrong  True does not mean it is correct or is accepted  It is a state where the opposite is always False  It is duality

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In some languages True is just and alias for the number   You can learn more why this is by reading more about boolean logic

[python] What does "while True" mean in Python?

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