What effect does the 'import' statement have in Python?

The 'import' statement in Python is designed to bring in external modules or packages into your program. This allows you to access functions, classes, and variables defined in those modules, enabling code reuse and enhancing the functionality of your program. By importing a module, you can utilize its pre-written code, which can save time and effort in development.

For instance, if you want to perform mathematical operations that are not built into the basic Python environment, you can import the math module. This gives you access to a wide range of mathematical functions, such as trigonometric functions, logarithms, and constants like pi.

The other options do not accurately describe the purpose of the 'import' statement. While creating a new variable or defining a main function are common programming concepts, they do not relate to importing external code. Similarly, the execution of a block of code pertains to control flow structures rather than the inclusion of modules or packages. Thus, the primary and correct function of the 'import' statement is to allow for the inclusion of additional functionalities through external modules.