Data structure initialization

Provides an empty container for storing key-value pairs.

Data processing: accumulating word counts; Web backend: initializing request cache; Configuration loading: building settings dictionary

Common in Python scripts, data processing pipelines, web backends, and any code that uses dictionaries for lookup or storage.

variable_name = {}

... = {}

variable_name: identifier

• dict methods like .update()
• .get()
• .keys()
• looping with for k
• v in dict.items()
• dictionary comprehensions

• Using dict() constructor: variable = dict()
• using literal with initial items: variable = {'key': value}

Confusing {} with empty set (which is set()); forgetting that {} creates dict, not set; using mutable default argument in function definitions.

Using set literal set() for empty set; using list [] for empty list; using collections.defaultdict for default values.

Coming from languages where braces denote blocks or objects (e.g., JavaScript, Java), may think {} creates an object with prototype; in Python it's a dict.

• dict literal
• dict constructor
• dict update
• dict comprehension

Note that {} creates a new empty dict each time; if used as a default argument, it leads to a shared mutable object across calls.

Provides a clean, hashable mapping for fast lookups and insertions.

Think of an empty phone book ready to fill with names and numbers.

Note that {} creates a new empty dict each time; if used as a default argument, it leads to a shared mutable object across calls.

Using dict comprehension or collections.defaultdict for default values.