List, Set and Dictionary Comprehensions

Python Tutorials - Herong's Tutorial Examples

∟List, Set and Dictionary Comprehensions

This chapter provides introductions and tutorial examples about list, set and dictionary comprehensions. Topics include introduction on list, set and dictionary comprehensions; examples of comprehensions with filtering conditions and nested loops, comparison of generator expressions and comprehensions.

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What Is Comprehension

What Is List Comprehension

What Is Filtered List Comprehension

What Is Double-List Comprehension

What Is Set Comprehension

What Is Dictionary Comprehension

Generator Expression vs. Comprehension

Takeaways:

A list comprehension creates a "list" object using a "for" clause enclosed in square brackets.
A set comprehension creates a "set" object using a "for" clause enclosed in braces.
A set comprehension creates a "dict" object using key:value pair expression and a "for" clause enclosed in braces.
A filtered comprehension is a comprehension with an "if" sub-clause to filter out items with a given condition.
A double comprehension is a comprehension that contains a double "for" clause to iterate two iterables as nested loops.
Generator expressions and list/set comprehensions have almost identical syntaxes: (EXPRESSION for ...) vs. [EXPRESSION for ...]/{EXPRESSION for ...}
Generator expressions return "generator" objects.
List/set/dictionary comprehensions return "list/set/dict" objects.
Generator expressions use "late-binding" to support next(generator) calls to reduce memory usage.