How to check whether a variable is a class or not

Question

I was wondering how to check whether a variable is a class  not an instance   or not   I ve tried to use the function isinstance object  class or type or tuple  to do this  but I don t know what type would a class will have   For example  in the following code  class Foo  pass   isinstance Foo             i want to make this return True    I tried to substitute   class  with      but I realized that class is a keyword in python

User · Answer

There are some working solutions here already  but here s another one    gt  gt  gt  import types  gt  gt  gt  class Dummy  pass  gt  gt  gt  type Dummy  is types ClassType True

User · Answer

This check is compatible with both Python 2 x and Python 3 x    import six isinstance obj  six class types    This is basically a wrapper function that performs the same check as in andrea crotti answer   Example    gt  gt  gt  import datetime  gt  gt  gt  isinstance datetime date  six class types   gt  gt  gt  True  gt  gt  gt  isinstance datetime date min  six class types   gt  gt  gt  False

User · Answer

simplest way is to use inspect isclass as posted in the most-voted answer  the implementation details could be found at python2 inspect and python3 inspect  for new-style class  isinstance object  type  for old-style class  isinstance object  types ClassType  em  for old-style class  it is using types ClassType  here is the code from types py   class  C      def  m self   pass ClassType   type  C

User · Answer

The inspect isclass is probably the best solution  and it s really easy to see how it s actually implemented  def isclass object          Return true if the object is a class       Class objects provide these attributes            doc           documentation string           module        name of module in which this class was defined        return isinstance object   type  types ClassType

User · Answer

This check is compatible with both Python 2 x and Python 3 x    import six isinstance obj  six class types    This is basically a wrapper function that performs the same check as in andrea crotti answer   Example    gt  gt  gt  import datetime  gt  gt  gt  isinstance datetime date  six class types   gt  gt  gt  True  gt  gt  gt  isinstance datetime date min  six class types   gt  gt  gt  False

User · Answer

isinstance X  type    Return True if X is class and False if not

User · Answer

There are some working solutions here already  but here s another one    gt  gt  gt  import types  gt  gt  gt  class Dummy  pass  gt  gt  gt  type Dummy  is types ClassType True

User · Answer

Benjamin Peterson is correct about the use of inspect isclass   for this job  But note that you can test if a Class object is a specific Class  and therefore implicitly a Class  using the built-in function issubclass  Depending on your use-case this can be more pythonic   from typing import Type  Any def isclass cl  Type Any        try          return issubclass cl  cl      except TypeError          return False   Can then be used like this    gt  gt  gt  class X            pass       gt  gt  gt  isclass X  True  gt  gt  gt  isclass X    False

User · Answer

gt  gt  gt  class X object           pass       gt  gt  gt  type X   lt type  type  gt   gt  gt  gt  isinstance X type  True

User · Answer

Benjamin Peterson is correct about the use of inspect isclass   for this job  But note that you can test if a Class object is a specific Class  and therefore implicitly a Class  using the built-in function issubclass  Depending on your use-case this can be more pythonic   from typing import Type  Any def isclass cl  Type Any        try          return issubclass cl  cl      except TypeError          return False   Can then be used like this    gt  gt  gt  class X            pass       gt  gt  gt  isclass X  True  gt  gt  gt  isclass X    False

User · Answer

gt  gt  gt  class X object           pass       gt  gt  gt  type X   lt type  type  gt   gt  gt  gt  isinstance X type  True

User · Answer

class Foo  is called old style class and class X object   is called new style class    Check this What is the difference between old style and new style classes in Python    New style is recommended  Read about  unifying types and classes

User · Answer

Even better  use the inspect isclass function    gt  gt  gt  import inspect  gt  gt  gt  class X object           pass       gt  gt  gt  inspect isclass X  True   gt  gt  gt  x   X    gt  gt  gt  isinstance x  X  True  gt  gt  gt  y   25  gt  gt  gt  isinstance y  X  False

User · Answer

simplest way is to use inspect isclass as posted in the most-voted answer  the implementation details could be found at python2 inspect and python3 inspect  for new-style class  isinstance object  type  for old-style class  isinstance object  types ClassType  em  for old-style class  it is using types ClassType  here is the code from types py   class  C      def  m self   pass ClassType   type  C

User · Answer

Even better  use the inspect isclass function    gt  gt  gt  import inspect  gt  gt  gt  class X object           pass       gt  gt  gt  inspect isclass X  True   gt  gt  gt  x   X    gt  gt  gt  isinstance x  X  True  gt  gt  gt  y   25  gt  gt  gt  isinstance y  X  False

User · Answer

class Foo  is called old style class and class X object   is called new style class    Check this What is the difference between old style and new style classes in Python    New style is recommended  Read about  unifying types and classes

User · Answer

gt  gt  gt  class X object           pass       gt  gt  gt  type X   lt type  type  gt   gt  gt  gt  isinstance X type  True

User · Answer

Even better  use the inspect isclass function    gt  gt  gt  import inspect  gt  gt  gt  class X object           pass       gt  gt  gt  inspect isclass X  True   gt  gt  gt  x   X    gt  gt  gt  isinstance x  X  True  gt  gt  gt  y   25  gt  gt  gt  isinstance y  X  False

User · Answer

The inspect isclass is probably the best solution  and it s really easy to see how it s actually implemented  def isclass object          Return true if the object is a class       Class objects provide these attributes            doc           documentation string           module        name of module in which this class was defined        return isinstance object   type  types ClassType

User · Answer

isinstance X  type    Return True if X is class and False if not

User · Answer

gt  gt  gt  class X object           pass       gt  gt  gt  type X   lt type  type  gt   gt  gt  gt  isinstance X type  True

User · Answer

class Foo  is called old style class and class X object   is called new style class    Check this What is the difference between old style and new style classes in Python    New style is recommended  Read about  unifying types and classes

User · Answer

class Foo  is called old style class and class X object   is called new style class    Check this What is the difference between old style and new style classes in Python    New style is recommended  Read about  unifying types and classes

User · Answer

Even better  use the inspect isclass function    gt  gt  gt  import inspect  gt  gt  gt  class X object           pass       gt  gt  gt  inspect isclass X  True   gt  gt  gt  x   X    gt  gt  gt  isinstance x  X  True  gt  gt  gt  y   25  gt  gt  gt  isinstance y  X  False

[python] How to check whether a variable is a class or not?

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