Python Underscores Part 3

Double leading and trailing underscores

__var__

When dealing with classes in Python, you're going to meet with these types of underscores a lot.

Interestingly, this typing is not affected by the interpreter but there're "magic methods" which reserve the use of those.

Examples:

__init__   <- for object constructors
__call__   <- for making objects 
                         callable
__str__    <- for returning 
              concise textual 
              representation of 
              an instance

...and many more

Since we have these methods with their corresponding names, we shouldn't use the double leading and trailing underscores when naming our variables.

Single underscores

_

For creating an insignificant(don't care) or a temporary variable that can be used in unpacking and other cases.

Ok, let's look at a simple example

Example:

student = ('Tom', 'Garfield', 18, 'CS') 
name, _, _, course = student
print(name) #Tom
print(course) #CS 
print(_) #18

Ready for something amazing?

In Python REPLs, single underscore is considered "special" and that represents the result of the last expression by the interpreter.

Example:

>>> 10 + 6 
16 
>>> _ 
16 
>>> print(_) 
16

It is also possible to create objects on the fly and play with them without naming them first.

Example:

>>> list() 
[] 
>>> _.append(1) 
>>> _.append(2) 
>>> _.append(3) 
>>> _ 
[1, 2, 3]
>>> _[1]
2

All of these could be a little difficult to get but after some rerepetitions, you would see how wonderful these can be.

Congrats on reaching this point.

Good luck and keep learning. 🚀