
Python Data Types – The Complete Guide for Beginners
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In Python, data types represent the kind of value a variable holds. Understanding data types is critical because Python is dynamically typed, meaning you don’t have to declare the type, but you still need to know what type of data you're working with.
This article will cover:
-
Built-in data types in Python
-
Type checking and conversion
-
Practical examples
-
Tips and common pitfalls
Why Data Types Matter
Data types:
-
Help the interpreter understand how to store and operate on data.
-
Allow you to apply appropriate operations (e.g., addition on numbers, concatenation on strings).
-
Prevent bugs by ensuring data is used correctly.
Categories of Python Data Types
Python’s built-in data types fall into the following categories:
Category | Types |
---|---|
Text | str |
Numeric | int , float , complex |
Sequence | list , tuple , range |
Mapping | dict |
Set | set , frozenset |
Boolean | bool |
Binary | bytes , bytearray , memoryview |
None Type | NoneType |
1. Text Type – str
A string is a sequence of Unicode characters.
name = "Alice"
message = 'Hello, world!'
You can access characters using indexing:
print(name[0]) # Output: A
2. Numeric Types – int
, float
, complex
-
int
: Whole numbers (positive, negative, or zero) -
float
: Numbers with decimals -
complex
: Numbers with real and imaginary parts
Examples:
a = 10 # int
b = 3.14 # float
c = 2 + 3j # complex
3. Sequence Types – list
, tuple
, range
list
: Mutable ordered collection
fruits = ["apple", "banana", "cherry"]
fruits[0] = "mango"
tuple
: Immutable ordered collection
dimensions = (1920, 1080)
range
: Generates a sequence of numbers
for i in range(5):
print(i)
4. Mapping Type – dict
A dictionary stores key-value pairs.
person = {
"name": "Alice",
"age": 30,
"city": "New York"
}
print(person["name"]) # Output: Alice
5. Set Types – set
, frozenset
-
set
: Unordered collection of unique items -
frozenset
: Immutable version of a set
my_set = {1, 2, 3, 2}
print(my_set) # Output: {1, 2, 3}
6. Boolean Type – bool
Represents truth values: True
or False
is_active = True
print(3 > 2) # Output: True
Used heavily in conditional statements.
7. Binary Types – bytes
, bytearray
, memoryview
Used for handling binary data (e.g., images, files):
binary_data = b"Hello"
mutable_bytes = bytearray(5)
8. None Type – NoneType
Represents the absence of a value:
value = None
Often used as default values in functions or placeholders.
Checking Data Types
Use the built-in type()
function:
x = 42
print(type(x)) # Output: <class 'int'>
Type Conversion
Convert one type to another using built-in functions:
int("10") # Output: 10
float("3.14") # Output: 3.14
str(100) # Output: "100"
list("abc") # Output: ['a', 'b', 'c']
Example: Working with Multiple Data Types
name = "John"
age = 25
height = 5.9
skills = ["Python", "Data Analysis"]
info = {"name": name, "age": age, "height": height, "skills": skills}
print(f"{info['name']} is {info['age']} years old and knows {', '.join(info['skills'])}.")
Output:
John is 25 years old and knows Python, Data Analysis.
Tips for Using Data Types
-
Use
type()
andisinstance()
to check data types. -
Use lists when data needs to change, tuples when it doesn't.
-
Use sets to remove duplicates quickly.
-
Use dictionaries for fast lookups by key.
-
Be careful when comparing different types (
int
vsstr
). -
Avoid using mutable types (like lists) as default arguments in functions.
⚠️ Common Mistakes
Mistake | Description |
---|---|
Mixing incompatible types | '3' + 4 raises a TypeError |
Using mutable types as keys | dict keys must be immutable |
Unexpected behavior with floats | 0.1 + 0.2 != 0.3 due to precision |
Modifying a tuple | Tuples are immutable |
Misusing identity is for equality == |
Use == for value comparison |
Summary
Type | Description | Example |
---|---|---|
str |
Text | "Hello" |
int |
Integer | 100 |
float |
Decimal | 3.14 |
list |
Mutable sequence | [1, 2, 3] |
tuple |
Immutable sequence | (1, 2, 3) |
dict |
Key-value pairs | {"name": "Alice"} |
set |
Unique values | {1, 2, 3} |
bool |
Boolean values | True |
None |
No value | None |
What's Next?
Once you're comfortable with data types, the next step is to explore:
-
Data structures (lists, dictionaries in depth)
-
Type hinting and annotations (Python 3.5+)
-
User-defined data types using classes
Tips and Tricks
What is pass in Python?
Python | Pass Statement
The pass statement is used as a placeholder for future code. It represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written.
def myfunction():
pass
How can you generate random numbers?
Python | Generate random numbers
Python provides a module called random using which we can generate random numbers. e.g: print(random.random())
We have to import a random module and call the random() method as shown below:
import random
print(random.random())
The random() method generates float values lying between 0 and 1 randomly.
To generate customized random numbers between specified ranges, we can use the randrange() method
Syntax: randrange(beginning, end, step)
import random
print(random.randrange(5,100,2))
What is lambda in Python?
Python | Lambda function
A lambda function is a small anonymous function. This function can have any number of parameters but, can have just one statement.
Syntex:
lambda arguments : expression
a = lambda x,y : x+y
print(a(5, 6))
It also provides a nice way to write closures. With that power, you can do things like this.
def adder(x):
return lambda y: x + y
add5 = adder(5)
add5(1) #6
As you can see from the snippet of Python, the function adder takes in an argument x and returns an anonymous function, or lambda, that takes another argument y. That anonymous function allows you to create functions from functions. This is a simple example, but it should convey the power lambdas and closures have.
What is swapcase() function in the Python?
Python | swapcase() Function
It is a string's function that converts all uppercase characters into lowercase and vice versa. It automatically ignores all the non-alphabetic characters.
string = "IT IS IN LOWERCASE."
print(string.swapcase())
How to remove whitespaces from a string in Python?
Python | strip() Function | Remove whitespaces from a string
To remove the whitespaces and trailing spaces from the string, Python provides a strip([str]) built-in function. This function returns a copy of the string after removing whitespaces if present. Otherwise returns the original string.
string = " Python "
print(string.strip())
What is the usage of enumerate() function in Python?
Python | enumerate() Function
The enumerate() function is used to iterate through the sequence and retrieve the index position and its corresponding value at the same time.
lst = ["A","B","C"]
print (list(enumerate(lst)))
#[(0, 'A'), (1, 'B'), (2, 'C')]
Can you explain the filter(), map(), and reduce() functions?
Python | filter(), map(), and reduce() Functions
- filter() function accepts two arguments, a function and an iterable, where each element of the iterable is filtered through the function to test if the item is accepted or not.
>>> set(filter(lambda x:x>4, range(7))) # {5, 6}
-
map() function calls the specified function for each item of an iterable and returns a list of result
>>> set(map(lambda x:x**3, range(7))) # {0, 1, 64, 8, 216, 27, 125}
-
reduce() function reduces a sequence pair-wise, repeatedly until we arrive at a single value..
>>> reduce(lambda x,y:y-x, [1,2,3,4,5]) # 3
Let’s understand this:
2-1=1
3-1=2
4-2=2
5-2=3Hence, 3.
What is a namedtuple?
Python | namedtuple
A namedtuple will let us access a tuple’s elements using a name/label. We use the function namedtuple() for this, and import it from collections.
>>> from collections import namedtuple
#format
>>> result=namedtuple('result','Physics Chemistry Maths')
#declaring the tuple
>>> Chris=result(Physics=86,Chemistry=92,Maths=80)
>>> Chris.Chemistry
# 92
Write a code to add the values of same keys in two different dictionaries and return a new dictionary.
We can use the Counter method from the collections module
from collections import Counter
dict1 = {'a': 5, 'b': 3, 'c': 2}
dict2 = {'a': 2, 'b': 4, 'c': 3}
new_dict = Counter(dict1) + Counter(dict2)
print(new_dict)
# Print: Counter({'a': 7, 'b': 7, 'c': 5})
Python In-place swapping of two numbers
Python | In-place swapping of two numbers
>>> a, b = 10, 20
>>> print(a, b)
10 20
>>> a, b = b, a
>>> print(a, b)
20 10
Reversing a String in Python
Python | Reversing a String
>>> x = 'PythonWorld'
>>> print(x[: : -1])
dlroWnohtyP
Python join all items of a list to convert into a single string
Python | Join all items of a list to convert into a single string
>>> x = ["Python", "Online", "Training"]
>>> print(" ".join(x))
Python Online Training
python return multiple values from functions
Python | Return multiple values from functions
>>> def A():
return 2, 3, 4
>>> a, b, c = A()
>>> print(a, b, c)
2 3 4
Python Print String N times
Python | Print String N times
>>> s = 'Python'
>>> n = 5
>>> print(s * n)
PythonPythonPythonPythonPython
Python check the memory usage of an object
Python | Check the memory usage of an object
>>> import sys
>>> x = 100
>>> print(sys.getsizeof(x))
28