How list is inserted into memory?

Question

list = ['xyz']
del list
print(list) #output <class 'list'>
print(type(list)) #output <class 'type'>
print([list].append(5)) #output None

a = 5
del a
print(a) #output error 'a' not defined

After deleting the list why python can still recognise it whereas python can not recognise the variable after deleting. Also when I did list.append(5) it shows error but [list].append(5) doesn’t show error.
Can someone help me with good tutorial/articles where these things are discussed in details?

Answer 1

Python should not allow builtIn types as variable names.

Answer 2

Try to use another name, not 'list', you will get the same error message as you did when you delete <a>.

list = ['xyz']
* Here you define a variable named <list>.

del list
* You delete the variable

print(list) #output <class 'list'>
* You print the type of `list`, it is a class

print(type(list)) #output <class 'type'>
* You print the type of the `list` class. In Python, all types are classes. A class is a type. Confused? so am I XD

print([list].append(5)) #output None
* append method of the `list` class returns nothing. It appends the argument to the object directly, not returning new object with the newly added value.

Answer 3

Thank you Ipang, Oma Falk, Theophile. Thanks for making it clear ^_^

Answer 4

Well there is a reason. "list" is part of the "__builtins__" module.
When you do :
list = [1, 2, 3]
You create a variable with the same name as the built-in type, but you do not replace it. Thus, if you do :
print(globals())
# {'list' : [1, 2, 3], '__builtins__' : <module 'builtins' (built-in)>}
The original 'list' variable is still part of the 'builtins' module.

When doing :
del list
You delete the first variable it finds in the global dict (and that's your [1, 2, 3] list).

After that :
print(list)
Python does not find any reference to "list" directly in the global dict, so it checks automatically the' builtins' module, and find the original list variable.