Objects vs instance in python

Question

In C++ there are just objects and classes, where objects are instances of classes.

In Python, a class definition (i.e., the body of a class) is called an object. And

Answer 1

Since you asked for "english please", I'll try to make it simple at the cost of detail.

Let's ignore classes and instances at first, and just look at objects.

A Python object contains data and functions, just like objects in every other object oriented programming language. Functions attached to objects are called methods.

x = "hello" #now x is an object that contains the letters in "hello" as data
print x.size() #but x also has methods, for example size()
print "hello".size() #In python, unlike C++, everything is an object, so a string literal has methods.
print (5).bit_length() #as do integers (bit_length only works in 2.7+ and 3.1+, though)

A class is a description (or a recipe, if you will) of how to construct new objects. Objects constructed according to a class description are said to belong to that class. A fancy name for belonging to a class is to be an instance of that class.

Now, earlier I wrote that in Python everything is an object. Well, that holds for stuff like functions and classes as well. So a description of how to make new objects is itself an object.

class C: #C is a class and an object
  a = 1

x1 = C() #x1 is now an instance of C
print x1.a #and x1 will contain an object a

y = C #Since C is itself an object, it is perfectly ok to assign it to y, note the lack of ()
x2 = y() #and now we can make instances of C, using y instead.
print x2.a #x2 will also contain an object a

print C #since classes are objects, you can print them
print y #y is the same as C.
print y == C #really the same.
print y is C #exactly the same.

This means that you can treat classes (and functions) like everything else and, for example, send them as arguments to a function, which can use them to construct new objects of a class it never knew existed.