Immutable or Mutable? Understanding Tuples in Python
Learn about immutable and mutable tuples in Python. Discover the advantages and disadvantages of using immutable objects, and explore a Pythonic alternative to mutable named tuples. Get the best practices for working with tuples in Python for better performance. Read more now.
Python is a widely used programming language that comes with a lot of unique features. One such feature is tuples. Tuples in Python are immutable objects, which means they cannot be changed once they are created. In this blog post, we will discuss the difference between immutable and mutable objects in Python and how to work with tuples.
Subheading 1: Tuples in Python are Immutable
Immutable objects are objects whose values cannot be changed after they are created. In Python, strings, numbers, and tuples are examples of immutable objects. Once a tuple is created, you cannot add, remove or modify any of its elements. This makes tuples useful for situations where you need to store a collection of values that should not be changed, such as coordinates or dates.
For example, suppose you have a tuple of coordinates representing a point in 2D space:
You can access the elements of the tuple using indexing:
x = point[0] # 3 y = point[1] # 4 However, you cannot change the values of the elements:
point[0] = 5 # TypeError: 'tuple' object does not support item assignment Advantages of using immutable objects include improved performance, thread safety, and easier debugging. Disadvantages include the inability to modify the object and the need to create a new object every time a change is required.
Subheading 2: Lists are Mutable, but List of Tuples can be Modified
Mutable objects are objects whose values can be changed after they are created. In Python, lists, sets, and dictionaries are examples of mutable objects. A list can contain elements of any type, including tuples. Although tuples themselves are immutable, a list of tuples can be modified.
For example, suppose you have a list of tuples representing students and their grades:
students = [('Alice', 87), ('Bob', 92), ('Charlie', 78)] You can access the elements of the list using indexing:
student1 = students[0] # ('Alice', 87) You can also modify the list by adding or removing elements:
students.append(('David', 82)) students.remove(('Charlie', 78)) However, you cannot modify the elements of the tuple:
student1[1] = 90 # TypeError: 'tuple' object does not support item assignment Subheading 3: Pythonic Alternative to Mutable Named Tuples
Named tuples are a convenient way to define a lightweight class in Python. However, they are immutable by default. The dataclasses module in Python 3.7 provides a Pythonic alternative to mutable named tuples.
For example, suppose you have a named tuple representing a point in 2D space:
from collections import namedtuplePoint = namedtuple('Point', ['x', 'y']) point = Point(3, 4) You can access the elements of the named tuple using dot notation:
x = point.x # 3 y = point.y # 4 However, you cannot change the values of the elements:
point.x = 5 # AttributeError: can't set attribute With the dataclasses module, you can define a mutable named tuple:
from dataclasses import dataclass@dataclass class Point: x: int y: intpoint = Point(3, 4) You can access and modify the elements of the mutable named tuple using dot notation:
Subheading 4: Understanding Ambiguity About Tuples in Python
Tuples in Python are often misunderstood as just immutable lists. However, they are more than that. Tuples can contain elements of any type, including other tuples. Tuples can also be used as keys in dictionaries, while lists cannot. Tuples also have an implicit packing and unpacking feature, which makes them useful for returning multiple values from a function.
For example, suppose you have a function that returns the quotient and remainder of two numbers:
def divmod(x, y): quotient = x // y remainder = x % y return quotient, remainderresult = divmod(10, 3) The function returns a tuple, which can be unpacked into two variables:
quotient, remainder = result Subheading 5: Strings are Immutable, but the Contents of a List Can Change
Strings in Python are also immutable objects. Once a string is created, it cannot be changed. However, the contents of a list can change. This can be confusing because a string can be converted to a list of characters, which can then be modified and converted back to a string.
For example, suppose you have a string:
You can convert the string to a list of characters:
You can convert the list back to a string:
However, you cannot modify the string itself:
s[1] = 'a' # TypeError: 'str' object does not support item assignment Tuples can contain mutable items, such as lists. This can be useful for situations where you need to store a collection of values that can be modified, but the tuple itself should not be modified.
In conclusion, tuples in Python are immutable objects, while lists are mutable objects. Tuples can contain elements of any type, including other tuples. Lists can contain elements of any type, including tuples. The dataclasses module in Python 3.7 provides a Pythonic alternative to mutable named tuples. Understanding the difference between immutable and mutable objects is important for writing efficient and bug-free Python code.
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