What is coded in python

When it is found during the execution of the loop, the current iteration stops and a new one begins with the updated value of the loop variable. In the example below, we skip the current iteration if the element is even and we only print the value if the element is odd:.

We just need to pass the sequences as arguments to the zip function and use this result in the loop. You can also keep track of a counter while the loop runs with the enum function. It is commonly used to iterate over a sequence and get the corresponding index. If you start the counter from 0 , you can use the index and the current value in the same iteration to modify the sequence:.

You can start the counter from a different number by passing a second argument to enumerate :. For loops also have an else clause. You can add this clause to the loop if you want to run a specific block of code when the loop completes all its iterations without finding the break statement.

In the example below, we try to find an element greater than 6 in the list. That element is not found, so break doesn't run and the else clause runs. However, if the break statement runs, the else clause doesn't run. We can see this in the example below:. While loops are similar to for loops in that they let us repeat a block of code.

The difference is that while loops run while a condition is True. In a while loop, we define the condition, not the number of iterations. The loop stops when the condition is False.

We can also use break and continue with while loops and they both work exactly the same:. We can also add an else clause to a while loop. If break is found, the else clause doesn't run but if the break statement is not found, the else clause runs.

In the example below, the break statement is not found because none of the numbers are even before the condition becomes False , so the else clause runs. But in this version of the example, the break statement is found and the else clause doesn't run:.

When we write and work with while loops, we can have something called an "infinite loop. This usually happens when the variables in the condition are not updated properly during the execution of the loop. You should see a KeyboardInterrupt message. We can write for loops within for loops and while loops within while loops. These inner loops are called nested loops. The inner loop completes two iterations per iteration of the outer loop.

The loop variables are updated when a new iteration starts. Here we have an example of nested while loops. In this case, we have to update the variables that are part of each condition to guarantee that the loops will stop. In Python, we can define functions to make our code reusable, more readable, and organized. This is the basic syntax of a Python function:. A function with no parameters has an empty pair of parentheses after its name in the function definition. A function with one or more parameters has a list of parameters surrounded by parentheses after its name in the function definition:.

When we call the function, we just need to pass one value as argument and that value will be replaced where we use the parameter in the function definition:. Here we have another example — a function that prints a pattern made with asterisks. You have to specify how many rows you want to print:. We can adapt the function that we just saw with one parameter to work with two parameters and print a pattern with a customized character:.

You can see the output with the customized character is that we call the function passing the two arguments:. Now you know how to define a function, so let's see how you can work with return statements. We will often need to return a value from a function. We can do this with the return statement in Python.

We just need to write this in the function definition:. Now we can call the function and assign the result to a variable because the result is returned by the function:. We can also use return with a conditional to return a value based on whether a condition is True or False. The Style Guide for Python Code recommends using return statements consistently.

It mentions that we should:. We can assign default arguments for the parameters of our function. In this example, we assign the default value 5 to the parameter b. If we omit this value when we call the function, the default value will be used. Else, you will see this error: SyntaxError: non-default argument follows default argument.

Here we have another example with the function that we wrote to print a pattern. A recursive function is a function that calls itself. These functions have a base case that stops the recursive process and a recursive case that continues the recursive process by making another recursive call. An error or unexpected event that that occurs while a program is running is called an exception.

Thanks to the elements that we will see in just a moment, we can avoid terminating the program abruptly when this occurs. In the example below, we will get a RecursionError. The factorial function is implemented recursively but the argument passed to the recursive call is n instead of n Unless the value is already 0 or 1 , the base case will not be reached because the argument is not being decremented, so the process will continue and we will get this error.

This way, the problem can terminate appropriately or even recover from the exception. For example, if we take user input to access an element in a list, the input might not be a valid index, so an exception could be raised:.

Because the except clause runs. However, if the value is valid, the code in try will run as expected. Instead of catching and handling all possible exceptions that could occur in the try clause, we could catch and handle a specific type of exception. We just need to specify the type of the exception after the except keyword:. We can specify a name for the exception object by assigning it to a variable that we can use in the except clause.

This will let us access its description and attributes. We can add an else clause to this structure after except if we want to choose what happens when no exceptions occur during the execution of the try clause:. If we enter the values 5 and 0 for a and b respectively, the output is:.

But if both values are valid, for example 5 and 4 for a and b respectively, the else clause runs after try is completed and we see:. We can also add a finally clause if we need to run code that should always run, even if an exception is raised in try.

In Object-Oriented Programming OOP , we define classes that act as blueprints to create objects in Python with attributes and methods functionality associated with the objects. The first line of the class definition has the class keyword and the name of the class:. In Python, we write class name in Upper Camel Case also known as Pascal Case , in which each word starts with an uppercase letter.

For example: FamilyMember. We are going to use the class to create object in Python, just like we build real houses from blueprints. The objects will have attributes that we define in the class. This is a method that runs when we create an instance of the class. We specify as many parameters as needed to customize the values of the attributes of the object that will be created. To create an instance of Dog , we need to specify the name and age of the dog instance to assign these values to the attributes:.

Some classes will not require any arguments to create an instance. In that case, we just write empty parentheses. We can also assign default values for the attributes and give the option to the user if they would like to customize the value. Now we can create a Circle instance with the default value for the radius by omitting the value or customize it by passing a value:. In Python, we don't have access modifiers to functionally restrict access to the instance attributes, so we rely on naming conventions to specify this.

For example, by adding a leading underscore, we can signal to other developers that an attribute is meant to be non-public. Class attributes are shared by all instances of the class. They all have access to this attribute and they will also be affected by any changes made to these attributes. This is the basic syntax of a method in a class. They may have zero, one, or more parameters if needed just like functions! For example, here is a bark method with no parameters in addition to self :.

It is recommended to add a space after the comma. Getters and setters are methods that we can define to get and set the value of an instance attribute, respectively. They work as intermediaries to "protect" the attributes from direct changes. In Python, we typically use properties instead of getters and setters. Let's see how we can use them. This method will act as a getter, so it will be called when we try to access the value of the attribute.

It is recommended to keep them as simple as possible. If we add descriptive print statements, we can see that they are called when we perform their operation:. Working with files is very important to create powerful programs. Let's see how you can do this in Python. In Python, it's recommended to use a with statement to work with files because it opens them only while we need them and it closes them automatically when the process is completed.

But this is already the default mode to open a file, so we can omit it like in the first example. We can iterate over the lines of the file using a for loop. The file path can be relative to the Python script that we are running or it can be an absolute path. There are two ways to write to a file. You can either replace the entire content of the file before adding the new content, or append to the existing content. To replace the content completely, we use the "w" mode, so we pass this string as the second argument to open.

We call the. When you run the program, a new file will be created if it doesn't exist already in the path that we specified. This small change will keep the existing content of the file and it will add the new content to the end. To delete a file with our script, we can use the os module. It is recommended to check with a conditional if the file exists before calling the remove function from this module:.

You might have noticed the first line that says import os. This is an import statement. Let's see why they are helpful and how you can work with them. Organizing your code into multiple files as your program grows in size and complexity is good practice. But we need to find a way to combine these files to make the program work correctly, and that is exactly what import statements do.

By writing an import statement, we can import a module a file that contains Python definitions and statements into another file. If we use this import statement, we will need to add the name of the module before the name of the function or element that we are referring to in our code:.

In our code, we can use the new name that we assigned instead of the original name of the module:. With this import statement, we can call the function directly without specifiying the name of the module:. This statement imports all the elements of the module and you can refer to them directly by their name without specifying the name of the module. According to the Style Guide for Python Code :. A really nice feature of Python that you should know about is list and dictionary comprehension.

This is just a way to create lists and dictionaries more compactly. List comprehensions are defined with square brackets []. This is different from generator expressions, which are defined with parentheses. They look similar but they are quite different. Let's see why. We can check this with the sys module. In the example below, you can see that their size in memory is very different:. We can use generator expressions to iterate in a for loop and get the elements one at a time.

But if we need to store the elements in a list, then we should use list comprehension. Now let's dive into dictionary comprehension. The basic syntax that we need to use to define a dictionary comprehension is:.

This is an example with a conditional where we take an existing dictionary and create a new dictionary with only the students who earned a passing grade greater than or equal to I really hope you liked this article and found it helpful. Now you know how to write and work with the most important elements of Python.

If you read this far, tweet to the author to show them you care. Tweet a thanks. Learn to code for free. Get started. Forum Donate. Estefania Cassingena Navone. Are you ready? Let's begin! Program in Python Before we start diving into the data types and data structures that you can use in Python, let's see how you can write your first Python program.

For example: "Hello, World! Quotes Within Strings If we define a string with double quotes "" , then we can use single quotes within the string. For example: "I'm 20 years old" If we define a string with single quotes '' , then we can use double quotes within the string. For example: 'My favorite book is "Sense and Sensibility"' String Indexing We can use indices to access the characters of a string in our Python program. String Slicing We may also need to get a slice of a string or a subset of its characters.

By default, it is the last character in the string if we omit this value, the last character will also be included. I'm learning Python. To define a list, we use square brackets [] with the elements separated by a comma. For example, here we have examples of lists: [1, 2, 3, 4, 5] ["a", "b", "c", "d"] [3. Here we have other valid examples: [["a", "b", "c"], ["d", "e", "f"], ["g", "h", "i"]] [1, [2, 3, 4], [5, 6, 7], 3.

Tuples in Python To define a tuple in Python, we use parentheses and separate the elements with a comma. The same principle and rules apply. Comparison Operator Chaining In Python, we can use something called "comparison operator chaining" in which we chain the comparison operators to make more than one comparison more concisely. The other operators perform an operation with the current value of the variable and the new value and assigns the result to the same variable.

Membership Operators You can check if an element is in a sequence or not with the operators: in and not in. In this case, the condition is False , so there is no output. True Condition Here we have another example. End When the condition of the if clause is True , this clause runs. False Condition Now the else clause runs because the condition is False. In this case, the output is: Hello!

Second Condition True If the first condition is False , then the second condition will be checked. End Multiple elif Clauses We can add as many elif clauses as needed. The range function in Python This function returns a sequence of integers that we can use to determine how many iterations repetitions of the loop will be completed. By default, it's 1. Python also has applications in Astronomy and Astrophysics. Let's see three of the main Python packages used in this scientific area:.

The Astropy package "contains various classes, utilities, and a packaging framework intended to provide commonly-used astronomy tools. Astropy is part of a larger project called The Astropy Project, which is "is a community effort to develop a common core package for Astronomy in Python and foster an ecosystem of interoperable astronomy packages. According to its About page, one of its goals is to "improve usability, interoperability, and collaboration between astronomy Python packages.

The SunPy package is described as "the community-developed, free and open-source solar data analysis environment for Python. The SpacePy package is "a package for Python, targeted at the space sciences, that aims to make basic data analysis, modeling and visualization easier.

According to its official Documentation :. According to the description of its GitHub repository , it has superposed epoch classes, drift shell tracing, access to magnetic field models, streamline tracing, bootstrap confidence limits, time and coordinate conversions, and more. There are many applications of Python in every area that you can possibly imagine. I hope that this article gave you an idea of the wide range of real-world applications of this programming language in industries that are currently shaping our world.

Remember that no matter which field you are in or which field you want to be in, learning Python will definitely open many doors for you.

It is here to stay. And it has transformed and improved our current world and it will continue to do so for many years. I really hope that you liked my article and found it helpful.

Check out my online courses. Follow me on Twitter. If you read this far, tweet to the author to show them you care. Tweet a thanks. Learn to code for free. Get started. Forum Donate. Estefania Cassingena Navone. Please take a moment to think about this question: How is Python applied in real-world scenarios? If you are learning Python and you want to know the answer, then this article is for you. Let's begin! Machine Learning. Web Development. Computer Science Education. Computer Vision and Image Processing.

Game Development. Medicine and Pharmacology. Biology and Bioinformatics. Neuroscience and Psychology. Other areas such as robotics, autonomous vehicles, business, meteorology, and graphical user interface GUI development.

Data Science Applications With a Python data visualization library, you can create a wide variety of plots and visual representations, such as: Lines, Bars, and Markers. Images, contours and fields. Subplots, axes and figures. Pie and polar charts. Libraries and Packages Let's see some of the most popular packages and libraries to work with Python in data science: Python for Data Analysis NumPy : this package is described as "the fundamental package for scientific computing with Python".

According to the official website of this package, "nearly every scientist working in Python draws on the power of NumPy. Seaborn : is "a Python data visualization library based on matplotlib. According to its official website: "you provide the data, tell ggplot2 how to map variables to aesthetics, what graphical primitives to use, and it takes care of the details.

Pandas : this library has many tools for data visualization. During the certification, you work on and complete these projects: Mean-Variance-Standard Deviation Calculator. Demographic Data Analyzer. Medical Data Visualizer. Page View Time Series Visualizer. Sea Level Predictor. Pandas "Getting Started" section: free introductory tutorials. NumPy Learn section : a curated collection of external resources to help you get started.

What is Machine Learning? One of the most amazing things about these systems is that they are continually refined. This is why we say that machines "learn" from the data.

This is very similar to what out brain does every single moment of every single day. Python and Machine Learning I'm sure you must be asking: what is the role of Python in this area? These are two other popular Python libraries used for Machine Learning: Keras — an open-source neural-network library written in Python. PyTorch — an open-source Machine Learning library used for developing and training neural networks.

For example, to give you an idea of the type of projects that you can create, freeCodeCamp's curriculum includes a free Machine Learning with Python Certification : Certification in freeCodeCamp's curriculum During the certification, you work on and complete these projects: Rock Paper Scissors. Cat and Dog Image Classifier. Book recommendation engine using K-Nearest Neighbors.

Linear Regression health costs calculator. Neural Network SMS classifier. More Examples of Real-World Applications You can find more examples of the applications of Machine Learning in Kaggle , an "online community of data scientists and machine learning practitioners" owned by Google.

To give you an idea of the type of projects that you can tackle with Machine Learning, previous competitions in Kaggle include: Predicting lung function decline. Predicting survival on the Titanic. Building tools for bird population monitoring. Labeling famous landmarks. Estimating the unit sales of Walmart retail goods. Identifying videos with face or sound manipulations. Predicting wait times at major city intersections. Detecting fraud from customer transactions.

Predicting a movie's worldwide box office revenue. Predicting pet adoption. Identifying risk when pilots are distracted, sleepy, or in other dangerous cognitive states. Python for Back-End Web Development In a web application, all the code used to interact with the user and create what the user sees is called the front-end part of the application. Web Frameworks These are some popular Python web frameworks: Django : a "high-level Python Web framework that encourages rapid development and clean, pragmatic design.

Pyramid : a "small, fast, down-to-earth Python web framework. Why Python? Python is so widely used as a teaching tool because: It is easy to learn: its syntax is simple and it can be learned quickly. Students start diving into more advanced aspects of computer science much more quickly than with other programming languages.

It is powerful: it is used in real-world applications, so students immediately start acquiring valuable skills for their careers. It is versatile: it supports various programming paradigms including imperative programming, functional programming, procedural programming, and object-oriented programming. Python in the Classroom and Online Learning Many universities and schools around the world have decided to teach introductory programming and computer science courses using Python.

It does this using the Python programming language, but the course also teaches programming concepts that can be applied in any other programming language. For example, freeCodeCamp's curriculum includes three free certificates with projects to help you expand your Python skills in key areas with high demand worldwide: Scientific Computing with Python.

Data Analysis with Python. Machine Learning with Python. Harvard University also offers these online courses that can be audited for free: CS50's Introduction to Computer Science. Image Processing Let's start with image processing. With a Python library, you can perform operations such as: Cropping, flipping, and rotating. Manipulating exposure and color channels. Detecting edges and lines. Adding filters and restoring images. Computer Vision Now let's dive into computer vision.

Some of them are: Navigation. Object and Event Detection. Facial recognition. Image classification. According to the " Using the Vision API with Python " tutorial in Google Codelabs, the Google Cloud Vision API: Allows developers to easily integrate vision detection features within applications, including image labeling, face and landmark detection, optical character recognition OCR , and tagging of explicit content.

Python Libraries These are some awesome libraries for computer vision and image processing: OpenCV : an "open source computer vision and machine learning software library". NumPy : it can be used to process the pixels of an image as a 2D array. SciPy : the scipy. Python Game Development Frameworks According to the official Python Documentation , there are two main Python frameworks used to develop games: pygame : "the original and still very much active package for game development using Python.

It allows Python to talk to SDL , a cross-platform, multimedia library. Because it needs to be compiled for each platform and each Python version, there can be a lag when a new Python version comes along. Because it is a pure Python package, it can be used as is even when a new Python version is released except for the Python 2 to Python 3 transition. Applications Some examples of the use of Python in medicine and pharmacology include: Making clinical diagnoses based on the patients' medical records and symptoms.

Analyzing medical data. Making computational models to speed up the process of development of new medications. Pharmaceutical Success Story: AstraZeneca According to the official Python Documentation , one of the world's leading pharmaceutical companies, AstraZeneca , used Python to improve their existing computational models to make them "more robust, extensible, and maintainable".

Python was chosen for this work because it is one of the best languages available for physical scientists, that is, for people who do not have a computer science background.

He stated that: Python was designed to solve real-world problems faced by an expert programmer. The result is a language that scales well from small scripts written by a chemist to large packages written by a software developer. It's intended for "precision medicine applications that revolve around genomics and proteomics". It works with reference and personalized genomes. MedPy : an open-source Python library "for medical image processing in Python, providing basic functionalities for reading, writing and manipulating large images of arbitrary dimensionality.

Biopython Biopython is a Python framework with "freely available tools for biological computation". Connect with biological databases. Work with phylogenetic trees and population genetics. Packages and Frameworks ProDy : a free and open-source package "for protein structural dynamics analysis" developed by Bahar Lab at the University of Pittsburgh.