6. Dynamic Imports

These examples show various ways to dynamically import modules, functions, or classes using importlib. This can be especially useful in scenarios like plugin systems, user-defined functionality, or optimizing performance by delaying imports.

1. Basic Dynamic Import of a Module

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import importlib

math_module = importlib.import_module("math")
print(math_module.sqrt(16))  # Output: 4.0

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2. Dynamically Import a Function from a Module

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import importlib

sqrt_function = getattr(importlib.import_module("math"), "sqrt")
print(sqrt_function(25))  # Output: 5.0

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3. Dynamic Import Using a User Input

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import importlib

module_name = input("Enter module name: ")  # e.g., "math"
function_name = input("Enter function name: ")  # e.g., "factorial"

module = importlib.import_module(module_name)
function = getattr(module, function_name)

print(function(5))  # For input "math" and "factorial", Output: 120

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4. Check if Module Exists Before Importing

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import importlib

module_name = "random"
try:
    module = importlib.import_module(module_name)
    print(f"Module '{module_name}' imported successfully.")
except ModuleNotFoundError:
    print(f"Module '{module_name}' not found.")

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5. Dynamic Import and Use of Class

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import importlib

module_name = "datetime"
class_name = "datetime"

module = importlib.import_module(module_name)
cls = getattr(module, class_name)
now = cls.now()

print(now)  # Output: Current date and time

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6. Dynamic Import with Fallback

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import importlib

module_name = "nonexistent_module"
try:
    module = importlib.import_module(module_name)
except ModuleNotFoundError:
    print(f"Module '{module_name}' not found. Falling back to 'math'.")
    module = importlib.import_module("math")

print(module.sqrt(9))  # Output: 3.0

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7. Dynamic Import of Multiple Modules in a Loop

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import importlib

modules = ["math", "random", "os"]
imported_modules = {}

for module_name in modules:
    imported_modules[module_name] = importlib.import_module(module_name)

print(imported_modules["math"].sqrt(16))  # Output: 4.0
print(imported_modules["random"].randint(1, 10))  # Random number between 1 and 10

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8. Dynamic Import and Method Call Using importlib

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import importlib

module_name = "os"
method_name = "getcwd"

module = importlib.import_module(module_name)
method = getattr(module, method_name)

print(method())  # Output: Current working directory

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9. Dynamic Import of a Custom Module

Suppose you have a file my_module.py with a function greet:

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# my_module.py
def greet(name):
    return f"Hello, {name}!"

You can dynamically import and use it:

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import importlib

module = importlib.import_module("my_module")
greet_function = getattr(module, "greet")

print(greet_function("Alice"))  # Output: Hello, Alice!

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10. Dynamic Import with Lazy Loading

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import importlib

def dynamic_import(module_name, func_name):
    module = importlib.import_module(module_name)
    return getattr(module, func_name)

# Import only when needed
sqrt_function = dynamic_import("math", "sqrt")
print(sqrt_function(49))  # Output: 7.0