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Python Function Tutorial – Part I

Python Function Tutorial – Part I

Posted December 13, 2019 at 9:47 am
Jay Parmar

Today, we will explore a remarkably handy feature seen in almost all programming languages: functions. There are lots of fantastic in-built functions in Python and its ecosystem. However, often, we as a Python programmer need to write custom functions to solve problems that are unique to our needs. Here is the definition of a function.

A function is a block of code(that performs a specific task) which runs only when it is called.

From the definition, it can be inferred that writing such block of codes, i.e. functions, provides benefits such as

  • Reusability: Code written within a python function can be called as and when needed. Hence, the same code can be reused thereby reducing the overall number of lines of code.
  • Modular Approach: Writing a python function implicitly follows a modular approach. We can break down the entire problem that we are trying to solve into smaller chunks, and each chunk, in turn, is implemented via a function.

We will go through the following points in this python functions tutorial:

  • Built-in python functions
  • User defined python functions
  • Variable Namespace and Scope
  • Lambda python functions

Python functions can be thought of as building blocks while writing a program, and as our program keeps growing larger and more intricate, functions help make it organized and more manageable. They allow us to give a name to a block of code, allowing us to run that block using the given name anywhere in a program any number of times. This is referred to as calling a python function. For example, if we want to compute the length of a list, we call a built-in len function. Using any python function means we are calling it to perform the task for which it is designed.

We need to provide an input to the len function while calling it. The input we provide to the python function is called an argument. It can be a data structure, string, value or a variable referring to them. Depending upon the functionality, a function can take single or multiple arguments.

In the next installment, the author will discuss the three types of python functions.

Visit for ready-to-use Python functions as applied in trading and data analysis.

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