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Mastering flat_map in Python with List Comprehension

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Introduction In Python, when working with nested lists or iterables, one common challenge is flattening them into a single list while applying transformations. Many programming languages provide a built-in flatMap function, but Python does not have an explicit flat_map method. However, Python’s powerful list comprehensions offer an elegant way to achieve the same functionality. This article examines implementation behavior using Python’s list comprehensions and other methods. What is flat_map ? Functional programming  flatMap is a combination of map and flatten . It transforms the collection's element and flattens the resulting nested structure into a single sequence. For example, given a list of lists, flat_map applies a function to each sublist and returns a single flattened list. Example in a Functional Programming Language: List(List(1, 2), List(3, 4)).flatMap(x => x.map(_ * 2)) // Output: List(2, 4, 6, 8) Implementing flat_map in Python Using List Comprehension Python’...
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Sets Vs Lists Python Programmer Tips

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Sets Vs Lists Python Programmer Tips


Sets are only useful when trying to ensure unique items are preserved. Before sets were available, it was common to process items and check if they exist in a list (or dictionary) before adding them.

List example


Here unique is an empty list. Every time I compare with this list, and if it is not duplicated then the input item will append to the unique list. 

>>> unique = [] 
>>> for name in ['srini', 'srini', 'rao', 'srini']:
 ... if name not in unique: 
... unique.append(name) 
... >>> unique ['srini', 'rao']


There is no need to do this when using sets. Instead of appending you add to a set:

Set example


>>> for name in ['srini', 'srini', 'rao', 'srini']:
... unique.add(name) 
... 
>>> unique {'srini', 'rao'}


Just like tuples and lists, interacting with sets have some differences on how to access their items. You can't index them like lists and tuples, but you can iterate over them without issues. 


The only reason I use sets is to ensure there aren't any duplicates. If that is not needed, a list is preferable.


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