You finished the last post. You stored your name in a variable. You stored your age. Both worked. But here's something that probably confused you. When you stored your name, you used quotes. When you stored your age, you didn't. And when you tried to combine them in a print statement, Python complained unless you added that str() thing. Why? Your name and your age are both just information. Why does Python care about the difference? Because to Python, they are not the same kind of thing at all. And understanding this, really understanding it, will save you from dozens of confusing errors in the future. By the end, you'll know: What data types are and why they exist The four main types you'll use constantly: strings, integers, floats, and booleans How to check what type something is How to convert between types Why type errors happen and how to read them Think about a calculator. You can add two numbers. You get a number back. Now try to add a name and a number. What's "Alex" plus 25? It makes no sense. There's no meaningful answer. Your calculator doesn't let you do that because it knows numbers and text are different kinds of things. Python thinks the same way. When Python stores a value, it doesn't just store the value. It also remembers what kind of value it is. A number behaves differently from text. A yes/no value behaves differently from a decimal. Tracking this is what types are for. There are four types you'll use in almost every program you ever write. Learn these four well before worrying about anything else. A string is any text. A name. A sentence. A word. An email address. A tweet. Even a single letter. name = "Akhil" city = "Mumbai" message = "I am learning Python" single_letter = "A" number_as_text = "42" The quotes are what make something a string. Single quotes or double quotes, both work. Pick one style and stick with it. name1 = "Akhil" # double quotes name2 = 'Akhil' # single quotes # both are identical strings Strings can be combined with +. This is called concatenation. You're just sticking text together. first = "Good" second = "morning" combined = first + " " + second print(combined) Output: Good morning You can also repeat a string with *. line = "-" * 20 print(line) Output: -------------------- Silly example but you'll actually use this to format output in real programs. One more thing. Strings have a length. len() tells you how many characters are in a string. name = "Jack" print(len(name)) Output: 4 An integer is any whole number. No decimals. No quotes. age = 25 score = 0 year = 2024 number_of_posts = 130 temperature = -5 Negative numbers work fine. Just put a minus sign. Integers support all the math you'd expect. a = 10 b = 3 print(a + b) # addition: 13 print(a - b) # subtraction: 7 print(a * b) # multiplication: 30 print(a / b) # division: 3.3333... print(a // b) # floor division: 3 (drops the decimal) print(a % b) # modulo: 1 (the remainder) print(a ** b) # power: 1000 (10 to the power of 3) Output: 13 7 30 3.3333333333333335 3 1 1000 The // operator is useful when you need a whole number result from division. The % operator gives you the remainder after division. You'll use both more than you think. A float is any number with a decimal point. price = 99.99 height = 5.11 pi = 3.14159 temperature = 36.6 small = 0.001 Floats work with all the same math operators as integers. price = 99.99 discount = 0.10 final = price - (price * discount) print(f"Final price: {final}") Output: Final price: 89.991 One thing to know. Computers store decimals in a way that sometimes causes tiny rounding errors. print(0.1 + 0.2) Output: 0.30000000000000004 That's not a bug in your code. That's how computers handle decimal math internally. For most purposes it doesn't matter. If you're building something that needs precise decimal handling, like financial software, Python has tools for that. But don't worry about it now. A boolean has exactly two possible values: True or False. Capital T and capital F. That's important. is_raining = True has_finished = False is_logged_in = True Booleans seem too simple to be useful. They're actually one of the most important types in programming. Every decision your code makes comes down to a boolean. Every if statement (which you'll learn in the next post) checks whether something is True or False. You can create booleans directly like above, or they come from comparisons. age = 25 print(age > 18) # True print(age == 30) # False print(age != 30) # True print(age str means string. int means integer. float means float. bool means boolean. You'll use type() a lot when debugging. When something behaves unexpectedly, checking what type it is often reveals the problem immediately. This is where a lot of beginner errors come from. Python won't automatically convert between types when it doesn't know what you want. You have to tell it. The conversion functions are str(), int(), and float(). age = 25 # integer age_as_text = str(age) # convert to string: "25" price_text = "99.99" # string price = float(price_text) # convert to float: 99.99 score_text = "42" # string score = int(score_text) # convert to integer: 42 A very common situation: you have a number you want to put inside a sentence. age = 25 message = "I am " + age + " years old" # this breaks Error: TypeError: can only concatenate str (not "int") to str Python says: you're trying to combine text and a number with +. I don't know what you want. I won't guess. Fix: age = 25 message = "I am " + str(age) + " years old" # works print(message) Output: I am 25 years old Or, the easier way, use an f-string. f-strings handle the conversion automatically. age = 25 print(f"I am {age} years old") # works, no str() needed Output: I am 25 years old Get comfortable with f-strings early. They prevent this whole category of errors. Mistake 1: Forgetting that numbers in quotes are strings age = "25" # this is a string, not a number next_year = age + 1 # breaks Error: TypeError: can only concatenate str (not "int") to str The number 25 is in quotes, so Python treats it as text. You can't do math with text. Fix: age = 25 # no quotes, it's a number now next_year = age + 1 # works: 26 Mistake 2: Using = instead of == when comparing age = 25 print(age = 25) # wrong Error: SyntaxError: invalid syntax = assigns. == compares. Use == to check if two things are equal. age = 25 print(age == 25) # correct: True Mistake 3: Wrong case on True and False is_done = true # wrong is_done = True # correct Python is case-sensitive. true is not the same as True. True with a capital T is the boolean. true with a lowercase t is just a variable name Python doesn't know about. Here's a short program that uses all four types. name = "Akhil" age = 25 height = 5.9 is_student = True print(f"Name: {name}") print(f"Age: {age}") print(f"Height: {height} feet") print(f"Is a student: {is_student}") print(f"Type of name: {type(name)}") print(f"Type of age: {type(age)}") next_age = age + 1 print(f"Next year I'll be {next_age}") greeting = "Hello, " + name + "!" print(greeting) Output: Name: Akhil Age: 25 Height: 5.9 feet Is a student: True Type of name: Type of age: Next year I'll be 26 Hello, Akhil! Type everything. Run it. Change the values. Break it on purpose. See what errors come up. Fix them. Create a file called types_practice.py. Make variables for all of this: Your full name (string) Your age (integer) Your height in any unit (float) Whether you have a pet (boolean) The year you were born (integer) Then: Print each one with a label using f-strings Calculate how many years until you turn 50 and print it Print the type of each variable using type() Expected output should look something like: Name: Akhilesh Yadav Age: 22 Height: 5.9 feet Has a pet: False Birth year: 1999 Years until 50: 25 Type of name: Type of age: Hints: subtraction works with -. The year you turn 50 is your birth year plus 50. You can store information now. The next step is making your code take different actions depending on what that information is. That's what if/else statements do, and it's where programming starts to feel like actual decision-making.