In this article, we are going to see Underscore (_) in Python.
Following are different places where “_” is used in Python:
- Single Underscore:
- Single Underscore in Interpreter
- Single Underscore after a name
- Single Underscore before a name
- Single underscore in numeric literals
- Double Underscore:
- Double underscore before a name
- Double underscore before and after a name
Single Underscore
Example 1: Single Underscore In Interpreter:
_ returns the value of the last executed expression value in Python Prompt/Interpreter
Example 2: Single Underscore for ignoring values
Multiple times we do not want return values at that time to assign those values to Underscore. It is used as a throw-away variable.
Python3
# Ignore a value of specific location/indexfor _ in range(10) print ("Test")# Ignore a value when unpackinga,b,_,_ = my_method(var1) |
Example 3: Single Underscore after a name
Python has theirs by default keywords which we can not use as the variable name. To avoid such conflict between python keyword and variable we use underscore after the name
Python3
class MyClass(): def __init__(self): print("OWK")def my_definition(var1=1, class_=MyClass): print(var1) print(class_)my_definition() |
Output:
1 <class '__main__.MyClass'>
Example 4: Single Underscore before a name
Leading Underscore before variable/function /method name indicates to the programmer that It is for internal use only, that can be modified whenever the class wants. Here name prefix by an underscore is treated as non-public. If specify from Import * all the names starting with _ will not import. Python does not specify truly private so this one can be called directly from other modules if it is specified in __all__, We also call it weak Private
Python3
class Prefix: def __init__(self): self.public = 10 self._private = 12test = Prefix()print(test.public)print(test._private) |
10 12
Example 5: Single underscore in numeric literals
The Python syntax is utilized such that underscores can be used as visual separators for digit grouping reasons to boost readability. This is a typical feature of most current languages and can aid in the readability of long literals, or literals whose value should clearly separated into portions.
Python3
# grouping decimal for easy readability of long literalsamount = 10_000_000.0# grouping hexadecimal for easy readability of long literalsaddr = 0xCAFE_F00D# grouping bits for easy readability of long literalsflags = 0b_0011_1111_0100_1110 |
Double underscore before a name
The leading double underscore tells the Python interpreter to rewrite the name in order to avoid conflict in a subclass. Interpreter changes variable name with class extension and that feature known as the Mangling.
Python3
class Myclass(): def __init__(self): self.__variable = 10 |
Calling from Interpreter
testFile.py
The Python interpreter modifies the variable name with ___. So Multiple times It uses as a Private member because another class can not access that variable directly. The main purpose for __ is to use variable /method in class only If you want to use it outside of the class you can make it public.
Python3
class Myclass(): def __init__(self): self.__variable = 10 def func(self) print(self.__variable) |
Calling from Interpreter
Double underscore before and after a name
The name starts with __ and ends with the same considering special methods in Python. Python provides these methods to use as the operator overloading depending on the user. Python provides this convention to differentiate between the user-defined function with the module’s function
Python3
class Myclass(): def __add__(self,a,b): print (a*b) |
Calling from Interpreter
