Interview-Questions-Python

How Python types can be splitted in two categories?
- Immutable types(tuple, str, int, float) We can't change the value of immutable type.
  The value of the variable changes, but it changes by changing what the variable refers to. A mutable type can change that way, and it can also change "in place". Consider following piece of code:
```
lst = []
s = ""
print(id(lst), id(s))
lst += [1]
s += 'bar' 
print(id(lst), id(s))  
```
  The value of id(lst) remains the same, while the id(s) changes because it refers to a new object.
- Mutable Types(list, dict, set) We can change the value of mutable type "in place".
What's decorator in Python? What the decorator should return? What are they used for?
A Python decorator is a specific change to the Python syntax that allows us to more conveniently alter functions and methods (and possibly classes in a future version). This is ideal when you need to extend the functionality of functions that you don't want to modify.
Decorator should return a "decorated" object. Actually, decorator is just a syntax sugar that can be changed to the following piece of code:
```
@change
def f(*args, **kwargs):
   pass
```
Is identical to:
```
def f(*args, **kwargs):
   pass
f = change(f)
```
In Python function are first class objects, they can be assigned, passed to another functions as arguments etc. Another important property to understanding decorators is closure . Which actually means that: Inner functions have access to the enclosing scope

https://www.thecodeship.com/patterns/guide-to-python-function-decorators/
What is generator? How it differs from iterator?
What's average lookup time in Python dict? Why can't we use mutable types as keys of dict?
What are metaclasses? What methods they should implement? Prepare method in metaclasses
What is Singleton? How would you implement it in Python?
How is implemented Python attribute access?
How modules are imported in Python? importlib

a = [0]
lst = [a]*5
lst[0].append(1)

How Python subclasses work? MRO

What will the following code produce?

class A(object):
    x = 1
 
class B(A):
    pass
 
class C(A):
    pass
 
print A.x, B.x, C.x
B.x = 2
print A.x, B.x, C.x
A.x = 3
print A.x, B.x, C.x

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Interview-Questions-Python