Python Flashcards

Question

What’s the difference between a method and a function?

Answer 1

A function is a standalone block of code you can call anywhere. A method is just a function that belongs to an object (inside a class) and usually works with that object’s data.

Answer 2

An instance is an individual object created from a class. It’s one product of that class/blueprint. An example or single occurrence of something.

Answer 3

An object is a specific thing created from a class that holds data (attributes) and can do actions (methods). It’s a product/instance of a class.

Answer 4

The 3 main conditional statements in Python are: if, elif, and else statements, used to control program flow based on conditions. if x == 7: print("Lucky number 7")

Answer 5

They are structures like if, elif, and else that execute code blocks based on whether conditions (which often use comparison operators) are True or False.

Answer 6

Comparison operators are symbols like ==, !=, <, >, <=, and >= that compare two values and return True or False. x = 10 print(x > 5) # True

Answer 7

elif is a Python keyword that means “else if.” It allows you to check multiple conditions sequentially after an initial if. x = 7 if x > 10: print("x is big") elif x == 7: print("x is seven") else: print("x is small")

Answer 8

else catches all other conditions not met by any previous if or elif checks. It’s the “catch-all” fallback in your conditional logic. x = 2 if x > 10: print("x is big") elif x == 7: print("x is seven") else: print("x is something else") If none of the earlier conditions are true, the else block runs.

Answer 9

Yes, Python is case SENSITIVE so it treats uppercase and lowercase letters as different. None, none, and NONE are not the same. x = None print(x) # Valid x = none # Error: 'none' is not defined

Answer 10

Identity operators are Python operators (is and is not) that check whether two variables refer to the same object IN MEMORY. x is y returns True if x and y are the same object. x is not y returns True if they are different objects.

Answer 11

not flips a True to False, or False to True. It reverses the condition so you can say “if NOT this, then do that.” not makes your code cleaner and easier to read when dealing with opposite conditions dynamically. Using not dynamically means you can invert whatever Boolean value a variable or expression currently holds at runtime, WITHOUT KNOWING or hardcoding its value before running. is_raining = get_weather_forecast() # Could be True or False dynamically if not is_raining: print("Go outside") else: print("Stay inside")

Answer 12

A for loop in Python is a control structure that repeats a block of code for each item in a sequence like a list, string, tuple, or range.

Answer 13

A while loop in Python is a control structure that repeats a block of code as long as a given condition is True. count = 3 while count > 0: print("Countdown:", count) count -= 1 Countdown: 3 Countdown: 2 Countdown: 1

Answer 14

The break statement in Python loops is used to immediately exit the loop, even if the loop condition is still true or items remain in the sequence.

Answer 15

The continue statement in Python loops is used to skip/bypass the rest of the current loop iteration and move on to the next one. for number in range(1, 6): if number == 3: continue # skip the rest of the loop when number is 3 print(number)

Answer 16

The else clause in Python loops is an optional block that runs after the loop finishes normally (not interrupted by break).

Answer 17

range() is used to generate a sequence of numbers for a for loop to iterate over.

Answer 18

1 3 5 range(1, 6, 2) means: start at 1, go up to (but not including) 6, stepping by 2 each time.

Answer 19

looping looping (count = 2 then 4 which is <3 so loop stops as condition no longer True)

Answer 20

7 range(7, 10, 2) starts at 7 and steps/increments by 3 but stops before reaching 10, so it only includes 7.

Answer 21

The condition if i % 5 == 0: checks if the variable i is divisible by 5 without any remainder, meaning i is a multiple of 5.

Answer 22

The modulo operator % in Python returns the remainder after dividing one number by another. 10 % 3 # Returns 1 because 10 divided by 3 is 3 with a remainder of 1

Answer 23

An object is an instance of a class containing actual data and can use the class’s methods.

Answer 24

Using curly braces {} with key-value pairs separated by colons. Example: my_dict = {"key1": "value1", "key2": "value2"}

Answer 25

A dictionary is a collection of key-value pairs where each key maps to a value. Keys are UNIQUE and IMMUTABLE. Dictionaries can be iterated over, just like a list. However, a dictionary, unlike a list, does not keep the order of the values stored in it.

Answer 26

By using the key inside square brackets: my_dict["key1"] # returns "value1"

Answer 27

my_dict["key3"] = "value3" If there already was a "key3" this same syntax would update/overwrite its value with "value3" from whatever it was before.

Answer 28

Use del or .pop(): del my_dict["key2"] value = my_dict.pop("key1")

Answer 29

It raises a KeyError. Use .get() to avoid this and return None or a default value instead: my_dict.get("missing_key", "default")

Answer 30

Use .items() method to iterate over key-value pairs in a dictionary {}: for key, value in my_dict.items(): print(key, value)

Answer 31

pop(key) removes the key-value pair for the specified key and returns the value. Raises KeyError if key not found unless a default is provided. value = my_dict.pop("key1") # removes "key1" and returns its value

Answer 32

del my_dict[key] removes the key-value pair for the specified key but does not return the value. Raises KeyError if key not found. del my_dict["key1"] # removes "key1" from the dictionary

Answer 33

Use pop() if you need the removed value. Use del if you just want to remove the key without caring about the value.

Answer 34

A module is a single Python file (.py) that contains variables, functions, and classes you can reuse.

Answer 35

Using the import statement. Example: import math or import math as mth Then can call its function via mth.sqrt() Etc.

Answer 36

A package is a folder containing multiple modules and an __init__.py file to group related modules together. __init__.py marks a directory as a Python package and can run initialization code for the package.

Answer 37

from module_name import function_name

Answer 38

from package_name import module_name

Answer 39

input() reads a line of text inputted by the user and returns it as a string.

Answer 40

A generator is a special type of function that YIELD items one at a time, creating an iterable sequence without storing the entire sequence in memory and pausing the function between calls to save memory. You then call each further iteration of the function with next() that continues from where the last yield left off. def ticket_machine(): yield 1 yield 2 yield 3 When you run this function, nothing happens yet. You have to call next() to get each value. gen = ticket_machine() print(next(gen)) # 1 print(next(gen)) # 2 print(next(gen)) # 3

Answer 41

For loops in Python are used to iterate over a SEQUENCE (like a list, string, or range) and run a block of code for each item in that sequence. for i in range(5): print(i)

Answer 42

Ordered and unordered data types in Python differ in how they store and access elements: Ordered data types (like list [], tuple (), str "", and dict {} in Python 3.7+) maintain the sequence of elements. You can access items by index or rely on their order. Example: my_list = [10, 20, 30] → my_list[0] is 10 Unordered data types (like set and dict pre-3.7 {}) do not guarantee any order. You can't rely on the position of elements. Example: my_set = {3, 1, 2} → order is unpredictable

Answer 43

A list comprehension is a faster way to create lists by applying an expression to each item in an iterable, optionally filtering items. squares = [x**2 for x in range(5)] # squares = [0, 1, 4, 9, 16] x squared = 0 squared = 0. 1 squared = 1 2 squared = 4 etc

Answer 44

Inheritance means a class (child/subclass) can reuse and extend the properties and methods of another class (parent/superclass). It lets you build on existing code without rewriting it. Inheritance lets you override or add new behavior while keeping the base functionality. class Animal: def speak(self): print("Animal speaks") class Dog(Animal): def speak(self): print("Woof!") dog = Dog() dog.speak() # Outputs: Woof!

Answer 45

OOP (Object-Oriented Programming) is about organizing your code around objects — things that combine data (attributes) and methods (functions attached to objects).

Answer 46

Encapsulation is the practice of bundling data and methods inside a class and hiding internal details from outside code.

Answer 47

Inheritance is when a subclass automatically gains attributes and methods from its parent class, enabling code reuse.

Answer 48

Same method name (e.g. speak()), different behavior depending on the object calling it (e.g. cat.speak() returns "meow" but dog.speak() returns "woof"). Polymorphism is when methods with the same name behave differently depending on the object calling them. Using the same method name on different objects, and each object runs its own version of that method.

Answer 49

Abstraction is exposing only essential features to outside code (code outside the classes scope) while hiding complex implementation details inside the class. class Dog: def speak(self): return "Woof!" class Cat: def speak(self): return "Meow!" for animal in [Dog(), Cat()]: print(animal.speak()) # Each object runs its own version of speak()

Answer 50

self is a reference to the current object (instance) of a class. It lets you access and modify that object's attributes and methods from within the class. Think of self as the word "this object". Used inside a class. Refers to the current object the method is acting on. class Car: def __init__(self, color): self.color = color # 'self.color' is the object's own color

Answer 51

super() is a built-in Python function that allows a subclass to call methods (usually __init__) from its parent class, enabling reuse of the parent’s code and proper initialization of inherited attributes. This means that you can use the parent classes' methods() from within a subclass/child-class without rewriting that code in each child-class/subclass.

Answer 52

Pass is a placeholder/skip statement in Python that does nothing when executed. It is used to keep the code syntactically correct when a statement is required but no action is needed or the code will be added later.

Answer 53

enumerate() is a built-in function that returns each item in a list along with its index, often used in for loops when you need both the item and its position. habits = ["Read", "Code", "Exercise"] for i, habit in enumerate(habits): print(f"{i+1}. {habit}")

Answer 54

String interpolation is the process of inserting values (variables, expressions) directly into a string, so the string dynamically includes those values. String interpolation name = "Alex" print("Hello, {}".format(name)) String interpolation has been superseced/improved by f-strings in newer Python versions!

Answer 55

f-strings are formatted string literals that allow embedding Python expressions inside strings using {} for easy and readable string interpolation. name = "Alice" age = 30 print(f"My name is {name} and I am {age} years old.") >>My name is Alice and I am 30 years old. The expressions in {} are evaluated and converted to strings and inserted into the output.

Answer 56

Use double braces {{ }} around the expression to show it literally, and single braces {} to evaluate it. Example: f"The expression {{2 + 2}} = {2 + 2}" outputs The expression {2 + 2} = 4.

Answer 57

Instance attributes are variables that belong to a specific object (instance) of a class. Each object can have different values for these attributes. class Car: def __init__(self, make, model): self.make = make # instance attribute self.model = model # instance attribute car1 = Car("Toyota", "Corolla") car2 = Car("Honda", "Civic") print(car1.make) # Toyota = differing instance attribute to the car 2 object/instance print(car2.make) # Honda

Answer 58

Class attributes are (constant) variables that are shared (the same) across all instances of a class. They are defined directly in the class, not inside the __init__ method. Use class attributes when: The value should be the same for all instances. You're storing shared data or constants. class Dog: species = "Canis familiaris" # class attribute def __init__(self, name): self.name = name # instance attribute dog1 = Dog("Buddy") dog2 = Dog("Max") print(dog1.species) # Canis familiaris print(dog2.species) # Canis familiaris

Answer 59

A Python decorator is a function that takes another function (or method) as input and returns a new function that adds some kind of functionality or behavior before or after the original function runs, without modifying the original function’s code. def my_decoratorFunction(func): def wrapper(): print("Before the function runs") func() print("After the function runs") return wrapper @my_decoratorFunction #applies the pre-defined decorator function/wrapper to say_hello() def say_hello(): print("Hello!") say_hello() Inbuilt decorator examples : @classmethod wraps a method so it gets the class (cls) instead of the instance (self). @staticmethod wraps a method to remove the automatic first argument altogether. @property wraps a method so you can access it like an attribute.

Answer 60

A staticmethod is a method inside a class that doesn’t receive self (instance) or cls (class) as its first argument. It behaves like a regular function but lives inside the class namespace. Their behaviour DOESN'T change based on object or class data. It's an inbuilt decorator function. @staticmethod class MathUtils: @staticmethod def add(a, b): return a + b print(MathUtils.add(5, 3)) # Output: 8

Answer 61

Instance methods depend on the particular object (instance) — they can access or modify the object’s attributes. Class methods depend on the class as a whole — they can access or modify class-level data. Static methods don’t depend on either; they’re just regular functions scoped inside the class for organization.

Answer 62

cls is the conventional name for the first parameter of a class method in Python. It refers to the class itself, not an instance of the class. cls=the current class object that the method belongs to.

Answer 63

for fruit, price in fruit_prices.items(): print(f"The price of {fruit} is {price}")

Answer 64

F-strings (formatted string literals) let you embed Python expressions inside strings using curly braces {}. They start with an f or F before the opening quote. name = "Alice" age = 30 print(f"{name} is {age} years old.") # Output: Alice is 30 years old.

Answer 65

C) The existing value is overwritten

Answer 66

{'a': 99, 'b': 2, 'c': 3}

Answer 67

C) update() update() merges another dictionary into the current one. It overwrites existing keys and adds new ones.

Answer 68

f-strings are a way to create strings with embedded Python expressions using {} — introduced in Python 3.6. They’re called “f-strings” because you start the string with an f"". name = "Alex" age = 25 print(f"My name is {name} and I'm {age} years old.") //My name is Alex and I'm 25 years old.

Python Flashcards

(95 cards)