Step 3 / Select topic Python Medium

What this bank covers

• Extended slicing: `seq[start:stop:step]`
• Comprehension scoping
• Late-binding closures
• Variadic positional parameters
• The context manager protocol
• Truthiness of containers
• The mutable default argument trap
• str.join(iterable)
• Variadic keyword parameters
• Format specification mini-language
• Generator functions are lazy
• Generator expressions vs list comprehensions
• Decorators are just function application
• functools.wraps
• Unpacking an iterable at a call site
• Unpacking a dict into keyword arguments
• f-strings evaluate arbitrary expressions
• Self-documenting f-strings
• Dict comprehensions
• Empty `{}` is a dict, not a set
• Multiple context managers in one `with`
• contextlib.contextmanager
• Exception chaining
• Custom exception classes
• @property
• Property setters
• @staticmethod
• @classmethod as alternate constructor
• enumerate() with a custom start
• zip() truncates to the shortest iterable
• sorted(..., key=...)
• sorted(..., reverse=True)
• collections.Counter
• collections.defaultdict
• collections.namedtuple
• itertools.chain
• itertools.combinations
• Shallow copy vs deep copy
• __repr__ as the fallback for __str__
• Default equality is identity
• functools.total_ordering
• Extended (starred) unpacking
• Walrus operator inside a comprehension filter
• Type hints are not enforced at runtime
• typing.Optional
• assert can be optimized away
• The global keyword
• The nonlocal keyword
• str.encode() and bytes.decode()
• is vs ==
• Hashability and dict keys
• Mixing positional and keyword arguments
• Chained comparisons
• Conditional (ternary) expressions
• Chained assignment shares one object
• Swapping via tuple unpacking
• String repetition with *
• List multiplication aliases inner mutable objects
• all() and any()
• map() is lazy
• filter() with None as the predicate
• lambda expression syntax
• dict.get(key, default)
• dict.setdefault(key, default)
• Dict union with |
• Set intersection operator
• frozenset immutability
• Strings are immutable
• list.append vs list.extend
• list.pop(index)
• del statement vs pop()
• Slice assignment can change list length
• Negative indexing
• range() is lazy
• Manual iterator protocol
• try/except/else
• Catching multiple exception types
• Bare raise re-raises the active exception
• pathlib.Path
• json.dumps / json.loads
• datetime + timedelta arithmetic
• random.seed()
• str.strip() default behavior
• startswith()/endswith() accept a tuple
• in operator on dicts checks keys
• Duck typing via __len__
• abc.ABC and @abstractmethod
• Class attributes vs instance attributes
• super() in __init__
• Nested unpacking
• Method chaining via returning self
• Comprehension with a filter clause
• Conditional expression inside a comprehension
• Nested (flattening) comprehension
• functools.reduce
• functools.partial
• zip(*pairs) as an unzip idiom
• Old-style % string formatting
• Returning multiple values as a tuple
• Keyword-only arguments with a bare *
• Mutable default arguments
• Changing a dict while iterating over it
• Queues: deque.popleft() versus list.pop(0)
• Lazy evaluation with next()