Python NeetCode

Vocabulary flashcards covering Python core concepts from the lecture notes.

print

Built-in Python function that outputs text to the console.

string

A sequence of characters defined with quotes; can use single or double quotes in Python.

quotes (single/double)

Strings can be defined with either single or double quotes in Python.

escape character

Backslash to include special characters inside strings (e.g., escaping quotes).

None

Python's absence-of-value marker; represented by the None keyword.

NoneType

The type of the None value.

dynamic typing

Python allows variable types to change over time.

static typing

Variable types are fixed; common in languages like Java and C++. Specifically contrasted with Python's dynamic typing.

type conversion

Changing a value from one type to another (e.g., int('10') -> 10, float(3)).

int()

Converts a value to an integer; truncates decimals.

float()

Converts a value to a floating point number.

bool

Boolean type; values are True or False.

NoneType

The type that represents the absence of a value (None).

type()

Built-in function that returns the data type of a value.

arithmetic operators

• (add), - (subtract), * (multiply), / (divide) in Python.

floor division

Operator //; divides and rounds down to an integer.

modulus

Operator %; returns the remainder after division.

exponent

Operator **; raises a number to a power.

shorthand operators

• =, -=, *=, /=; modify a variable in place.

PEMDAS

Order of operations: parentheses, exponents, multiplication/division, addition/subtraction.

execution order

Code runs top-to-bottom unless control structures change flow.

list

Mutable, ordered collection of items; denoted with [ … ].

tuple

Immutable, ordered collection; denoted with ( … ).

dictionary

Key-value mapping; denoted with { key: value }.

set

Unordered collection of unique elements; created with set() or braces.

mutable vs immutable

Mutable (lists, dicts) can change; immutable (strings, tuples) cannot.

slice

Subsequence extraction using start:end:step notation.

negative indexing

Accessing elements from the end using negative indices (e.g., -1 for last element).

range

Function to generate a sequence of numbers for loops; end is exclusive.

index

Position of an element in a sequence; zero-based indexing.

len()

Returns the length of a sequence (string, list, etc.).

string concatenation

Joining strings using the + operator.

substring

A portion of a string obtained via slicing.

first n characters

s[:n] returns the first n characters of s.

last n characters

s[-n:] returns the last n characters of s.

string immutability

Strings cannot be modified in place; operations return new strings.

list append

Add an element to the end of a list.

list pop

Remove and return the last element; can specify index to remove.

in operator

Membership test; x in list/dict/set checks presence.

dictionary keys

Unique keys in a dictionary; used to access values.

dictionary values

Values stored in a dictionary; accessed via dict.values().

dictionary items

Key-value pairs; accessed via dict.items().

try/except

Error handling structure to catch and handle exceptions.

ValueError

Error raised when an operation receives an argument of the right type but inappropriate value.

ZeroDivisionError

Error raised when dividing by zero.

split

String method to split a string into a list using a delimiter.

read input

input() reads a line from standard input as a string.

parse input

Splitting a string (e.g., by comma) to convert into data structures.

read integers

Read a line, split by delimiter, convert each piece to int.

exception handling specificity

You can have specific except blocks (e.g., ValueError) and a generic one.

default argument

A function parameter with a default value; optional when calling the function.

type hints

Optional annotations declaring expected parameter and return types.

NoneType in hints

When a function returns nothing, the annotated return type can be None.

if statement

Conditional execution block; runs when the condition is true.

elif

Else-if branch in Python; additional condition checks.

else

Fallback block executed if previous conditions were false.

comparison operators

Operators like ==, !=,

logical operators

And, or, not; combine boolean expressions.

truthy/falsy

Truthiness: non-false values evaluate to True; falsy values evaluate to False.

default value order

Non-default parameters must come before default ones in function definitions.

for loop

Iterates over a sequence or range; uses range() for numeric ranges.

while loop

Repeats while a condition is true; requires careful increment to avoid infinite loops.

break

Terminate the nearest enclosing loop immediately.

continue

Skip the rest of the current loop iteration and continue.

pass

No-op placeholder; allows empty blocks without errors.

substring slicing rules

End index is non-inclusive; s[start:end] yields characters from start up to end-1.

reverse with slicing

Use [::-1] to reverse a string or sequence.

default parameter order rule

If a parameter has a default value, all following parameters must also have defaults.

split vs join

Split creates a list from a string; join combines a list of strings into one string.

enumerating dictionaries

Using for key in dict iterates keys; dict.items() yields (key, value) pairs.

importance of indentation

Indentation defines code blocks in Python; incorrect indentation causes errors.