New function in builtins

November 1, 2021

Accessing Builtins

Python builtins module contains functions and constants. These functions and constants are available in the interpreter and can be accessed via their name.

>>> max
<built-in function max>
>>> __debug__
True
>>> Ellipsis
Ellipsis
>>>

Buitlins can be accessed via __builtins__ variable.

>>> __builtins__.max
<built-in function max>
>>> __builtins__.Ellipsis
Ellipsis

You can also access bulitins from builtins module.

>>> import builtins
>>> builtins.max
<built-in function max>
>>> builtins.Ellipsis
Ellipsi

Setting functions and variables in builtins

Python import system is executed only once. A variable or reference to a name can be set to buitlins module and can be accessed afterwards. For example, you can add reference to a function palindrome and can be accessed later in the program.

Here is a simple example.

first.py defines a function palindrome.
first.py assigns the function reference palindrome to the builtins module.
first.py imports is_palindrome from the second.py file.
first.py calls is_palindrome function.
is_palindrome function internally calls palindrome function.

# first.py 
def palindrome(name: str) -> bool:
    return name[::-1] == name


__builtins__.palindrome = palindrome

def greet():
    pass

from second import is_palindrome

print("is malayalam palindrome:", is_palindrome("malayalam"))
print("is tamil palindrome:", is_palindrome("tamil"))

# second.py
def is_palindrome(name: str) -> bool:
    return palindrome(name)

try:
    print(greet())
except NameError:
    print('greet function is not visible')

$ python3 first.py 
greet function is not visible
is malayalam palindrome: True
is tamil palindrome: False

For example, ipython shell sets display function in the IPython shell. Source