Python for a Java developer 
I will share my learning curve and unthinkable points of python as a java developer.
When I had started python, I already had 2years of experience in java. So it was very uncomfortable to get into the python world. In this series, I will explain things a java developer will never think about when coding.
Today [part 1] I will explain two topics ,
- The use of underscore ( _ )
- List Comprehension [Inline list operations]
USE OF UNDERSCORE(_):
Skipping a value:
We can skip a value assignment by using underscore in place of a variable name.For example.
We can skip multiple element using star(*) operator before underscore (_).Here we are skipping [2,3,4,5,6].
For a list of tuples we can ignore key(considering first element as key) if we don’t need it ,like in the last two lines in the below image explains a function don’t need the keys of tuples so we skip it,
In Object Oriented Part:
Double leading and trailing underscore:
Few special methods use this format like,
- __init__ ,Constructor of the class
- __len__ , We override this method to return custom value for len(MyClassObject).
- __file__ ,Can give you the current python file location.
- __eq__ , is executed for any custom objects of Mycalass a and Myclass b, when a==b type expressions are executed. In a word you override __eq__ when you need any (==) operation is needed for your class.
Also, a single underscore before field’s name or a method’s name inside class indicates private field or method.In above example _a is a private field.
We use logical ,mathematical operation on a list to get a new list in a single line. Soooo.. convenient, if we understand it.
For a list of [1,2,3,4,5] we can set “G” for an element ,greater than 3 and set “S” for an element ,less than or equal to 3 in then modified new list.For example.
Here we square each element of list l containing [1,2,3,4,5].
Unpacking List of Tuples
We can only take list of values or keys from list of tuples:
Nested List operation
We can perform nested list operation as shown below.Here we perform a matrix transpose.
This was a small overview of use of underscore and list comprehension feature of python.Please use python documentations for more deep knowledge.Hope you like it .