python data types
Python Data Types
What is a Data Type?
A data type defines the kind of value a variable can store.
Python automatically determines the data type when a value is assigned.
Numeric Data Types
Integer (int)
Stores whole numbers.
age = 25
temperature = -10
print(type(age))
Output:
<class 'int'>
Float (float)
Stores decimal numbers.
price = 99.99
pi = 3.14159
print(type(price))
Output:
<class 'float'>
Complex (complex)
Stores complex numbers.
num = 3 + 4j
print(num)
print(type(num))
Output:
(3+4j)
<class 'complex'>
Boolean Data Type
Boolean (bool)
Stores either True or False.
is_logged_in = True
is_admin = False
print(type(is_logged_in))
Output:
<class 'bool'>
String Data Type
String (str)
Stores text data.
name = "John"
print(type(name))
Output:
<class 'str'>
Sequence Data Types
List (list)
Ordered and mutable collection.
fruits = ["Apple", "Banana", "Mango"]
print(type(fruits))
Output:
<class 'list'>
Modifying List
fruits[0] = "Orange"
print(fruits)
Output:
['Orange', 'Banana', 'Mango']
Tuple (tuple)
Ordered but immutable collection.
numbers = (10, 20, 30)
print(type(numbers))
Output:
<class 'tuple'>
Common Tuple Mistake
❌ Wrong
numbers = (10, 20, 30)
numbers[0] = 100
Output:
TypeError
Range (range)
Represents a sequence of numbers.
numbers = range(5)
print(list(numbers))
Output:
[0, 1, 2, 3, 4]
Set Data Types
Set (set)
Unordered collection of unique values.
numbers = {1, 2, 3, 4}
print(type(numbers))
Output:
<class 'set'>
Duplicate Values Removed
numbers = {1, 1, 2, 2, 3}
print(numbers)
Output:
{1, 2, 3}
Frozen Set (frozenset)
Immutable version of a set.
data = frozenset([1, 2, 3])
print(data)
Output:
frozenset({1, 2, 3})
Mapping Data Type
Dictionary (dict)
Stores data as key-value pairs.
student = {
"name": "John",
"age": 21
}
print(type(student))
Output:
<class 'dict'>
Accessing Values
print(student["name"])
Output:
John
Binary Data Types
Bytes (bytes)
Immutable binary data.
data = b"Hello"
print(data)
Output:
b'Hello'
Bytearray (bytearray)
Mutable binary data.
data = bytearray([65, 66, 67])
print(data)
Output:
bytearray(b'ABC')
Memory View (memoryview)
Provides memory access without copying.
data = memoryview(bytes(5))
print(data)
Output:
<memory at ...>
None Data Type
NoneType
Represents no value.
value = None
print(type(value))
Output:
<class 'NoneType'>
User Defined (Custom) Data Types
Python allows creation of custom data types using classes.
Example
class Student:
pass
s1 = Student()
print(type(s1))
Output:
<class '__main__.Student'>
Summary of Built-in Data Types
| Category | Data Types |
|---|---|
| Numeric | int, float, complex |
| Boolean | bool |
| Text | str |
| Sequence | list, tuple, range |
| Set | set, frozenset |
| Mapping | dict |
| Binary | bytes, bytearray, memoryview |
| Special | NoneType |
Common Data Type Mistakes
Mistake 1: Mixing String and Number
❌ Wrong
age = 20
print("Age: " + age)
Output:
TypeError
✅ Correct
age = 20
print("Age: " + str(age))
Mistake 2: Assuming List and Tuple are Same
❌ Wrong
data = (1, 2, 3)
data[0] = 10
Output:
TypeError
Type Casting and Type Conversion
What is Type Casting?
Converting one data type into another.
Integer to String
age = 25
text_age = str(age)
print(text_age)
print(type(text_age))
Output:
25
<class 'str'>
String to Integer
age = "25"
number = int(age)
print(number)
Output:
25
Integer to Float
num = 10
result = float(num)
print(result)
Output:
10.0
Float to Integer
price = 99.99
result = int(price)
print(result)
Output:
99
Note: Decimal part is removed, not rounded.
String to Float
num = "25.5"
print(float(num))
Output:
25.5
List to Tuple
numbers = [1, 2, 3]
print(tuple(numbers))
Output:
(1, 2, 3)
Tuple to List
numbers = (1, 2, 3)
print(list(numbers))
Output:
[1, 2, 3]
Common Type Casting Mistakes
Mistake 1
❌ Wrong
int("10.5")
Output:
ValueError
✅ Correct
int(float("10.5"))
Output:
10
Mistake 2
❌ Wrong
int("hello")
Output:
ValueError
String Functions
upper()
Converts to uppercase.
name = "python"
print(name.upper())
Output:
PYTHON
lower()
name = "PYTHON"
print(name.lower())
Output:
python
title()
name = "python programming"
print(name.title())
Output:
Python Programming
capitalize()
name = "python"
print(name.capitalize())
Output:
Python
swapcase()
name = "PyThOn"
print(name.swapcase())
Output:
pYtHoN
strip()
text = " hello "
print(text.strip())
Output:
hello
lstrip()
text = " hello"
print(text.lstrip())
Output:
hello
rstrip()
text = "hello "
print(text.rstrip())
Output:
hello
replace()
text = "I like Java"
print(text.replace("Java", "Python"))
Output:
I like Python
split()
text = "apple,banana,mango"
print(text.split(","))
Output:
['apple', 'banana', 'mango']
join()
items = ["Apple", "Banana", "Mango"]
print("-".join(items))
Output:
Apple-Banana-Mango
find()
text = "Python"
print(text.find("t"))
Output:
2
index()
text = "Python"
print(text.index("t"))
Output:
2
startswith()
print("Python".startswith("Py"))
Output:
True
endswith()
print("Python".endswith("on"))
Output:
True
count()
text = "banana"
print(text.count("a"))
Output:
3
isalpha()
print("Python".isalpha())
Output:
True
isdigit()
print("123".isdigit())
Output:
True
isalnum()
print("Python123".isalnum())
Output:
True
center()
print("Python".center(20))
Output:
Python
zfill()
print("10".zfill(5))
Output:
00010
Difference Between Function and Method
Function
A function is an independent block of code.
Example:
numbers = [1, 2, 3]
print(len(numbers))
Output:
3
Here:
len()
is a function.
Method
A method belongs to an object.
Example:
name = "python"
print(name.upper())
Output:
PYTHON
Here:
upper()
is a method.
Function vs Method
| Function | Method |
|---|---|
| Independent | Belongs to an object |
| Called directly | Called using dot notation |
| Example: len() | Example: upper() |
| Works on data passed to it | Works on the object itself |
Example Comparison
Function
numbers = [1, 2, 3]
print(len(numbers))
Method
name = "python"
print(name.upper())
Homework 1
Identify the data type:
a = 10
b = 10.5
c = "Python"
d = [1, 2, 3]
e = (1, 2, 3)
Solution
print(type(a))
print(type(b))
print(type(c))
print(type(d))
print(type(e))
Homework 2
Convert:
"100"
into integer.
Solution
num = int("100")
print(num)
Homework 3
Convert:
"python programming"
into:
PYTHON PROGRAMMING
Solution
text = "python programming"
print(text.upper())
Homework 4
Count the number of "a" characters in:
"banana"
Solution
print("banana".count("a"))
Output:
3
Homework 5
Replace:
Java
with
Python
in:
I love Java
Solution
text = "I love Java"
print(text.replace("Java", "Python"))
Output:
I love Python
Summary
| Topic | Key Concept |
|---|---|
| Data Types | Type of data stored |
| Type Casting | Convert one type to another |
| String Functions | Manipulate text |
| Function | Independent block of code |
| Method | Function attached to an object |
Master these topics before moving to:
- Operators
- Conditional Statements
- Loops
- Functions
- Modules
- Exception Handling
- Object-Oriented Programming