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The ultimate security is your understanding of reality. – H. Stanley Judd This article will introduce the basics of Python HTTP programming. So far in this series, we have discussed Python security programming and Python network programming. In this article the reader will learn how to implement advanced Python HTTP-related scenarios and use cases.  A web server is a computer server which stores content related to the web.  Websites are hosted on this type of server. Web servers are used for other purposes such as FTP, email, gaming, storage and more. Server is typically a term used for hardware and software. Hardware based web servers handle HTML pages, images, style sheets, javascript, and web server software. The server can handle data exchange with devices connected to the internet. Web server software consists of user management, user access, and a server based on HTTP protocol. HTTP based servers can parse URLs which are web addresses. HTTP is the protocol used for browsing and rendering web content. Web sites are browsed by searching through domain names of the web servers. The web servers store web content and have domain names configured for the network DNS ip address. A website has a group of web pages serving images, videos and audio content. An HTTP request is created by the browser to request web content on the web server. The web server returns the HTTP response by sharing the requested content with the URL. The response is generated by invoking a server side component which interacts with the database. A web server is called static if the content is shared as it is available on the server. The examples are images, videos and audio files. On the other hand, a dynamic web server has a static module and a dynamic module rendering the response from the server side components. The architectural approaches used for a web server are concurrent and single process event driven architectural patterns. A concurrent approach can process many HTTP requests simultaneously. This can be achieved by web servers with multiple threads, processes, and hybrid approaches of processes and threads. A simple web server creates a single thread. The single thread spawns multiple child processes for HTTP requests. The child processes handle the HTTP requests for further processing required for rendering the response. Multiple Processed based web servers have a master slave pattern based implementation. In this implementation, the master process manages the load by having child processes forked. Multiple Thread based servers manage multiple threads to handle concurrent requests. The hybrid approach is to have multiple processes created and threads being spawned by each process. The diagram below shows the request and response mechanism implemented in the web server.  Web Server Architecture The web server listens to HTTP requests on a TCP IP Address and a port number. It responds to the HTTP request by sending the HTTP response. The HTTP headers have the source and destination information for requests and responses. A web server is yet another network server which can handle requests and responses. The web server acts as a request dispatcher and handlers are provided to render the response. The code samples below show advanced Python HTTP scenario implementation. In this implementation, we look at the basic example in which Python is used for an HTTP web server. Prerequisites: 1. You need to set up Python3.5 to run the code samples below. You can download from this link. Problem Http.server and socket server module has the features to create a TCP server and handling of HTTPRequests. The features related to HTTPServer implementation and client connection are shown in the example below.  The code snippet below shows the Python web server using HTTP API. import http.server import socketserver HTTPPORT = 8000 HTTPRequestHandler = http.server.SimpleHTTPRequestHandler with socketserver.TCPServer(("", HTTPPORT), HTTPRequestHandler) as httpd: print("web server started", HTTPPORT) httpd.serve_forever() HTTPRequestHandler of http.server module  is used to handle the requests and serve the files from the directory of the web server. TCPServer of socket server module is used to create an HTTP web server httpd. This server receives and sends httprequests and httpresponses respectively using TCP protocol. HTTP is a TCP protocol. It is an application layer protocol. The web server is instantiated with an IP address and port number. The handler is passed, which is a Simple HTTPRequestHandler. serve_forever method is on httpd. This method is used to start the web server. The web server receives the requests  and sends the responses which are HTTP protocol messages. HTTP webserver is started by executing the commands shown below. Instructions for Running the Code #running the python web server python3 web_server.py Output Further in this series, we are going to cover network traffic analysis, information gathering from servers, FTP, SSH & SNMP interaction, cryptography, nmap scanning, geolocation & metadata retrieval, and  vulnerability scanning and analysis. The post Python Networking : HTTP Programming appeared first on Topcoder.

In the world of software development, the design system is not new. Frequently, Topcoder contests involve system design and some even require us to create a design system for a particular company. Therefore it helps us learn how to apply it to our work. Through this blog post we will learn what a design system is, remind you of its benefits and see the best examples available. What is the Design System? A design system is a set of components that can be reused in different combinations. The design system allows you to manage designs on a large scale. Design systems contain a comprehensive guide to project design – a collection of rules, principles, constraints, and best practices. The core element of the design system is often the UI Component Library. These UI elements are also their representations implemented in code. Benefits of Design Systems? In the initial phase before designing, a design system does look complicated and like you will expend a lot of effort to create it. However, after it is built, the design of the system can save you a lot of time in future product development. The following are some of the main benefits of creating a system design. Consistency With a design system and front end designer, the developer will be able to implement a consistent UI much more easily. They can think of certain pages as sets of components. Example: Developers don’t have to think that this is a button with a # ff6600 background, a Proxima Nova Bold 12pt font, and 4px padding. The engineer knows that this is just the Main Button, and he uses this component in a few pages. Consistency gives the impression of higher quality. QA specialists can easily monitor designs that are implemented with the design system documentation. Inconsistencies should rarely occur. Better Communication The creation of a design system fosters better communication with the development team. Since the design system is the only source of truth, this means it contains vocabulary that can be used in the project. When developers and designers discuss the page, they will use the same component name. Thanks to this you will not talk about “this little purple button,” but “the secondary button.” Many errors occur due to misunderstanding, but a design system allows you to speak with the same naming conventions throughout the project. Faster Process You have built or purchased a UI control library that is needed to implement the UI. Now you only use it when new features require the creation of new pages or modification of existing ones. Even if you decide to build a UI library from scratch, a lot of time spent on this task will allow you to quickly create UI for new features. Focus More on UX Using the UI library means you don’t need to re-learn each time what the input field should look like on this page – it’s already been determined. Visuals were previously explained in the system – now you can put together new pages with them and focus more on better usability and creating a pleasant experience. What is in the Design System? The fundamental purpose of the design system is to facilitate teamwork and to match the values and images that are being shared by organizations or companies. Therefore, the following things must exist in the design system that you are building. Values, Vision, and Mission of the Company Every organization and company must have a value and purpose in the formation of the company. Therefore, before a design system is created, it is important to align the team around a set of shared goals that are clearly in line with company objectives. This will help build the vision and make sure everyone looks toward the same direction. These goals will develop over time and that is normal. The capabilities of the design system must ensure that change is widely communicated. As for values, they are the big ideas that will guide your choices, in accordance with brand goals. We need to ensure that the design system that we create is no different from these key values. Design Principle Design principles must guide design choices. Design principles are far more than just the visual aspects of a product. Design principles are guiding sentences that help teams to achieve product goals because of the design. They will help the team to make meaningful design decisions. As an example, on the Medium site, one of their design principles is “Direction of choice”. Thanks to that principle, instead of designing a plain text editor with unlimited color and font choices, they chose a simpler one. That allows the writer to focus on the content of the article rather than the visual aspect. Brand Identity & Language Identity must be defined in line with brand strategy and objectives. There are several elements that can shape the identity and language of your brand including: ColorFontsSpaceShapeIconIllustrationTaking picturesAnimationSound and toneSounds These brand elements will require several rules that will form the system. In the design system, this is realized by guidelines: do’s and don’ts and good examples of use. This will ensure the design team uses the right combination of language. If this is done correctly the brand will be very unique and easily recognizable. Components & Patterns Components and patterns are at the heart of the system. All the elements mentioned earlier will help us to make the system and provide a consistent experience. Components are used in Sketch by the designer, and directly in the code by the developer. Their functional behavior must be determined. As for patterns, they are building instructions that will allow us to use the components logically and consistently, across all products. Best Practice In addition to documentation, which is often directly linked to the system, best practices will accompany the team in a larger and more transverse manner. The idea is to explore general best practices and extract only those that make sense, based on the product and the level of maturity of the team. Best practices will help teams to form and develop their technical skills. What Design System Characteristics Does Your Organization or Company Need? Many of the design system characteristics that we see are scattered throughout the internet. All the characteristics of a design system are built according to the needs of the organization. The following are some examples of character design systems that you can apply to your organization. Tight or Loose System The strict system will have comprehensive and detailed documentation and will be fully synchronized between design and development. There will be a rigorous process for introducing new patterns in the system. A strict system must be very broad to cover most cases that the team might face. A loose system will leave more room for experimentation. The system is here to provide a framework for the team while maintaining freedom. Designers and developers are free to use it or not, regarding their specific needs for the product being built. You have to find the right balance between rigorous and flexible: a very strict system might be opposed by designers and developers who don’t want to use it. On the other hand, if the design system is too loose, the character of your organization or company will look uneven in the products being built. Modular or Integrated Modular systems are made of interchangeable and reusable parts. This is suitable for projects that have to scale quickly and which have to adapt to various user needs. The negative part of a modular system is that it is often more expensive to realize (because it can be difficult to make modules that can be independent while working well together). This kind of system will be especially suitable for large-scale products such as e-commerce, financial and government websites. For modular systems, it would be very interesting to work with the atomic design in mind. Integrated systems focus on one unique context. Integrated systems also consists of parts, but these parts will not be interchangeable. This type of system is compatible with products that have very few repeatable components and which require strong and frequently changing art direction. Centralized or Distributed Model The organization around the design system is very important for its evolution and scalability. In a centralized model, one team is responsible for the system and makes it grow. This team is in place to facilitate the work of other teams and must work closely with them to ensure that the system covers most of their needs. In the distributed model, several people from several teams are responsible for the system. The adoption of the system is faster because everyone feels involved but it also requires a team leader who will maintain overall vision. In each case, it’s best if everyone participates and makes suggestions to improve the system, to create a sense of ownership. Whatever system design you are going to build, first make sure to answer the questions listed below. How big is your organization or company? How many people will use your design system?How familiar are the teams in your organization or company with the design system?What variety of products or methods of development will be aligned with the design system to be created? What level of consistency does our product require? Examples of Existing Design Systems Take a look at these design systems that have been created by some of the world’s top companies. Although we realize that some of these companies created their systems through many hours of work, this is provided publicly. Please learn and create a new design system that suits the style of your organization or company. Material Design This is one of the most popular systems. It was formed over the years but is now used not only by the Google Team but also by many makers of Android and Web Applications. Atlassian Design System One of the most complete on the market used in real products made by Atlassian. Polaris Design system created by Shopify Carbon System design made by IBM Human Interface Guide Apple prepared the design system for all of its platforms Grommets The design system by Hewlett-Packard is presented in a very friendly way. Conclusion Knowledge of system design is one of the important elements that you must have in this era. The design system is a complete product, which will help project actors to build other products. With the design system, the product development process will be more effective, have good quality, and will have a DNA that is suitable for the company. The post Design Systems 101 appeared first on Topcoder.

Source: LinkedIn Public Company Page

Easy To start, we can try all one-digit and two-digit numbers to be sure to get rid of all special cases. (There aren’t really any special cases other than n=10 with product 0, but why not be extra safe.) If a bigger number is the optimal answer, then clearly: it does not contain the digit 0 (product 0 was already obtained for n=10)its digits are sorted in nondecreasing order (because rearranging digits leaves the same product but makes the number bigger) The count of such numbers is very small and we can generate and test all of them. More precise math: if you are generating 18-digit numbers with non-decreasing digits from [1-9], the count is binomial(18+8,8) = about 1.5 million, because each number corresponds to some sequence of 18 “print” and 8 “inc” commands. If you want to go beyond the task, a nice exercise is to look for as many ways to speed up the search as you can. To list some: After n=11 you don’t need the digit 1, as it does not change the product. The number will never contain combinations of digits like 22 or 23 (can be replaced by 4 or 6). Combinations like 25 will give you n=0 in two steps, so they are also useless for bigger goals. The most fun is that there are still open problems related to this simple task. In particular, we do not know whether the sequences are actually infinite. For base = all zeros, the last term we know is actually the last one you found while solving the task. We know that if there are other terms, they have at least tens of thousands of digits, and it is conjectured that the sequence is actually finite. See http://oeis.org/A003001 for more. Medium The biggest part of solving this task is in finding a general construction that is reasonably easy to implement. Below is a sample figure showing the construction used by the reference solution. Essentially, I always use some points on the current line that are just to the right of the input to “eat” the empty space on the line above that one. This way I’m sure I won’t get any accidental grid points into the polygon: there aren’t any between two consecutive rows. The checker for this problem was also fun to write. I used winding number for the point-in-polygon check, and Pick’s theorem as an easy way to check whether your polygon doesn’t contain any other grid points on the inside. Hard The key observation is that the number of Hamiltonian cycles has to be small. Why? If we only have one root + (N-1) leaves, we have N distinct Hamiltonian cycles starting at the root and going “to the right”. More precisely, once we choose the edge along which the cycle leaves the root, the only option is to do N-1 jumps and then to use the neighboring edge to return to the root. (The tiniest tree is a special case, as both choices produce the same cycle. This was shown in the examples and it was easy to handle.) If we have a deeper tree, observe a deepest leaf Y. It has a parent X that is not the root, and a sibling Z that is also a leaf. We have a triangle XYZ in our graph, and there are only three other outgoing edges: from Y to the previous leaf, from Z to the next leaf, and from X to its parent. Thus, the Hamiltonian cycle has to pass through this triangle exactly once, and the previous and next vertex on the cycle will uniquely determine the order in which it visits X, Y, and Z. Hence, we can imagine that we contract XYZ into a single new node. Any Hamiltonian cycle in the new graph will correspond to exactly one cycle in the old graph and vice versa. The previous argument can be repeated until we get a tree that is just root + leaves. Thus, the total number of cycles is just 2 (directions of traversal) * N (starting points) * degree of the root <= 2 * 250 * 249. In order to generate all cycles, probably the easiest implementation is using three recursive functions: “traverseLeafLeaf”, “traverseLeafRoot”, and “traverseRootLeaf” that return the unique path that traverses an entire subtree from leftmost leaf or root to rightmost leaf or root. Then, we just sort everything, check whether the index is small enough, and output the corresponding sequence. The post 2019 Topcoder Open Algorithm Round 4 appeared first on Topcoder.

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