How do I get the opposite negation of a Boolean in Python

Question

For the following sample   def fuctionName int  bool       if int in range               if bool    True              return False         else              return True   Is there any way to skip the second if-statement  Just to tell the computer to return the opposite of the boolean bool

User · Answer

You can just compare the boolean array  For example  X    True  False  True    then  Y   X    False   would give you  Y    False  True  False

User · Answer

If you are trying to implement a toggle  so that anytime you re-run a persistent code its being negated  you can achieve that as following   try      toggle   not toggle except NameError      toggle   True   Running this code will first set the toggle to True and anytime this snippet ist called  toggle will be negated

User · Answer

The not operator  logical negation   Probably the best way is using the operator not    gt  gt  gt  value   True  gt  gt  gt  not value False   gt  gt  gt  value   False  gt  gt  gt  not value True   So instead of your code   if bool    True      return False else      return True   You could use   return not bool   The logical negation as function  There are also two functions in the operator module operator not  and it s alias operator   not   in case you need it as function instead of as operator    gt  gt  gt  import operator  gt  gt  gt  operator not  False  True  gt  gt  gt  operator not  True  False   These can be useful if you want to use a function that requires a predicate-function or a callback   For example map or filter    gt  gt  gt  lst    True  False  True  False   gt  gt  gt  list map operator not   lst    False  True  False  True    gt  gt  gt  lst    True  False  True  False   gt  gt  gt  list filter operator not   lst    False  False    Of course the same could also be achieved with an equivalent lambda function    gt  gt  gt  my not function   lambda item  not item   gt  gt  gt  list map my not function  lst    False  True  False  True    Do not use the bitwise invert operator   on booleans  One might be tempted to use the bitwise invert operator   or the equivalent operator function operator inv  or one of the other 3 aliases there   But because bool is a subclass of int the result could be unexpected because it doesn t return the  inverse boolean   it returns the  inverse integer     gt  gt  gt   True -2  gt  gt  gt   False -1   That s because True is equivalent to 1 and False to 0 and bitwise inversion operates on the bitwise representation of the integers 1 and 0   So these cannot be used to  negate  a bool   Negation with NumPy arrays  and subclasses   If you re dealing with NumPy arrays  or subclasses like pandas Series or pandas DataFrame  containing booleans you can actually use the bitwise inverse operator     to negate all booleans in an array    gt  gt  gt  import numpy as np  gt  gt  gt  arr   np array  True  False  True  False    gt  gt  gt   arr array  False   True  False   True     Or the equivalent NumPy function    gt  gt  gt  np bitwise not arr  array  False   True  False   True     You cannot use the not operator or the operator not function on NumPy arrays because these require that these return a single bool  not an array of booleans   however NumPy also contains a logical not function that works element-wise    gt  gt  gt  np logical not arr  array  False   True  False   True     That can also be applied to non-boolean arrays    gt  gt  gt  arr   np array  0  1  2  0    gt  gt  gt  np logical not arr  array   True  False  False   True     Customizing your own classes  not works by calling bool on the value and negate the result  In the simplest case the truth value will just call   bool   on the object   So by implementing   bool    or   nonzero   in Python 2  you can customize the truth value and thus the result of not   class Test object       def   init   self  value           self  value   value      def   bool   self           print    bool   called on   r   format self           return bool self  value         nonzero       bool      Python 2 compatibility      def   repr   self           return   self   class     name     self  value r    format self self    I added a print statement so you can verify that it really calls the method    gt  gt  gt  a   Test 10   gt  gt  gt  not a   bool   called on Test 10  False   Likewise you could implement the   invert   method to implement the behavior when   is applied   class Test object       def   init   self  value           self  value   value      def   invert   self           print    invert   called on   r   format self           return not self  value      def   repr   self           return   self   class     name     self  value r    format self self    Again with a print call to see that it is actually called    gt  gt  gt  a   Test True   gt  gt  gt   a   invert   called on Test True  False   gt  gt  gt  a   Test False   gt  gt  gt   a   invert   called on Test False  True   However implementing   invert   like that could be confusing because it s behavior is different from  normal  Python behavior  If you ever do that clearly document it and make sure that it has a pretty good  and common  use-case

User · Answer

The accepted answer here is the most correct for the given scenario    It made me wonder though about simply inverting a boolean value in general  It turns out the accepted solution here works as one liner  and there s another one-liner that works as well  Assuming you have a variable  n  that you know is a boolean  the easiest ways to invert it are   n   n is False   which was my original solution  and then the accepted answer from this question   n   not n   The latter IS more clear  but I wondered about performance and hucked it through timeit - and it turns out at n   not n is also the FASTER way to invert the boolean value

User · Answer

You can just use   return not bool

User · Answer

Python has a  not  operator  right  Is it not just  not   As in     return not bool

User · Answer

Another way to achieve the same outcome  which I found useful for a pandas dataframe  As suggested below by mousetail  bool 1 - False   bool 1 - True

[python] How do I get the opposite (negation) of a Boolean in Python?

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