Python Topics

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Language Core Checklist

• First-class functions, higher-order functions, pure functions
• Functional tools — map, filter, reduce
• Generators & yield
• Generator expressions
• Enums
• ord(), chr()
• Decorators — 3-level nested pattern, functools.wraps
• OOP — classes, __init__, self, instance vs class variables
• Encapsulation (__private)
• Inheritance & super()
• Polymorphism, operator overloading (__add__, __eq__, etc.)
• Context managers (with, __enter__/__exit__)
• Abstract classes (abc.ABC, @abstractmethod)
• Dataclasses (@dataclass)
• Type hints & typing module
• *args / **kwargs
• List/dict/set comprehensions
• lambda functions
• itertools / functools

Python for DSA (Interview-Specific)

# Useful built-ins
sorted(lst, key=lambda x: x[1])     # sort by second element
heapq.nlargest(k, lst)              # top-k
collections.Counter(lst)            # frequency map
collections.defaultdict(list)       # graph adjacency list
collections.deque(maxlen=k)         # sliding window / BFS queue
bisect.bisect_left(lst, target)     # binary search on sorted list

# Infinity
float('inf')   # positive
float('-inf')  # negative

# Integer division / modulo
7 // 2   # 3
7 % 2    # 1
divmod(7, 2)  # (3, 1)

# String tricks
''.join(lst)           # join list of chars
s[::-1]                # reverse string
ord('a'), chr(97)      # char ↔ int

# Swap without temp
a, b = b, a

Libraries Checklist

• logging — levels, handlers, structured logging
• os / pathlib — file system operations
• json — serialize/deserialize
• datetime — dates, timezones
• re — regex
• requests / httpx — HTTP clients
• asyncio — async/await, event loop
• pytest — testing
• pydantic — data validation (heavily used in FastAPI / LangChain)
• FastAPI — async web framework
• SQLAlchemy — ORM

Interview Topics (Python-Specific)