How do I use a Boolean in Python

Question

Does Python actually contain a Boolean value  I know that you can do   checker   1 if checker       dostuff   But I m quite pedantic and enjoy seeing booleans in Java  For instance   Boolean checker  if  someDecision        checker   true    if checker          some stuff     Is there such a thing as a Boolean in Python  I can t seem to find anything like it in the documentation

User · Answer

Yes  there is a bool data type  which inherits from int and has only two values  True and False    But also Python has the boolean-able concept for every object  which is used when function bool  x   is called   See more  object nonzero and boolean-value-of-objects-in-python

User · Answer

Boolean types are defined in documentation  http   docs python org library stdtypes html boolean-values Quoted from doc   Boolean values are the two constant objects False and True  They are used to represent truth values  although other values can also be considered false or true   In numeric contexts  for example when used as the argument to an arithmetic operator   they behave like the integers 0 and 1  respectively  The built-in function bool   can be used to cast any value to a Boolean  if the value can be interpreted as a truth value  see section Truth Value Testing above   They are written as False and True  respectively   So in java code remove braces  change true to True and you will be ok

User · Answer

The boolean builtins are capitalized  True and False   Note also that you can do checker   bool some decision  as a bit of shorthand -- bool will only ever return True or False   It s good to know for future reference that classes defining   nonzero   or   len   will be True or False depending on the result of those functions  but virtually every other object s boolean result will be True  except for the None object  empty sequences  and numeric zeros

User · Answer

checker   None   if some decision      checker   True  if checker        some stuff    Edit   For more information  http   docs python org library functions html bool  Your code works too  since 1 is converted to True when necessary  Actually Python didn t have a boolean type for a long time  as in old C   and some programmers still use integers instead of booleans

User · Answer

Unlike Java where you would declare boolean flag   True  in Python you can just declare myFlag   True  Python would interpret this as a boolean variable

User · Answer

Booleans in python are subclass of integer  Constructor of booleans is bool  bool class inherits from int class   issubclass bool int     will return True  isinstance True bool    isinstance False bool    they both True  True and False are singleton objects  they will retain same memory address throughout the lifetime of your app  When you type True  python memory manager will check its address and will pull the value  1   for False its value is  0   Comparisons of any boolean expression to True or False can be performed using either is  identity  or     equality  operator  int True     1 int False     0  But note that True and  1  are not the same objects  You can check   id True     id 1     will return False  you can also easily see that   True  gt  False    returns true cause 1 gt 0  any integer operation can work with the booleans    True   True   True  3   All objects in python have an associated truth value  Every object has True value except   None  False  0 in any numeric type  0 0 0 0 0j etc   empty sequences  list  tuple  string   empty mapping types  dictionary  set  etc   custom classes that implement   bool   or   len   method that returns False or 0    every class in python has truth values defined by a special instance method     bool   self    OR    len    When you call bool x  python will actually execute  x   bool       if instance x does not have this method  then it will execute  x   len      if this does not exist  by default value is True  For Example for int class we can define bool as below    def   bool   self         return self    0  for bool 100   100   0  will return True  So bool 100     True you can easily check that bool 0  will be False  with this for instances of int class only 0 will return False  another example  bool  1 2 3    1 2 3  has no   bool     method defined but it has   len     and since its length is greater than 0  it will return True  Now you can see why empty lists return False

User · Answer

True     and False obviously   Otherwise  None evaluates to False  as does the integer 0 and also the float 0 0  although I wouldn t use floats like that   Also  empty lists     empty tuplets     and empty strings    or    evaluate to False   Try it yourself with the function bool     bool     bool   a value    bool     bool  A string   bool True      -  bool False  bool 0  bool None  bool 0 0  bool 1    etc

[python] How do I use a Boolean in Python?

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