Invoking an external command in Python is a two step process:

from subprocess import call
call(["ls","-1"])

Learning SQL development can seem like an overwhelming task at first. However, mastering just a few key points will help ease your way through 80 percent of the day-to-day challenges when writing stored procedures and solving common problems. Here are three important SQL development factors to keep in mind:

Outer Joins
One of the most crucial things to understand in SQL server are joins. Joins are a way to retrieve data from two or more tables based on logical relationships between them. Joins dictate how Microsoft SQL Server ought to use data from one table to select the rows in another table.

In my experience inner joins are intuitive while outer joins can present additional hours of grief by overlooking associations in the other table(s). The outer join is the key to answering questions about what the database does not have. For example, if you need to make a query to display all the students who are without report-cards, you’ll need a left join to get all students coupled with a “where clause” to return the ones who have nulls for their report card table columns in the results.

Many talented Java script programmers have muddled through the SQL Server by deficient coding around the inner join. As a result, their queries can take five hours to run, whereas, properly written left joins, can take only two seconds to run.

Aggregation
Grouping results comes up in SQL a lot more than you might think. Knowing how to write a query when answering questions such as, “What’s the average grade for each teacher’s student list?” is invaluable. This kind of question cannot be answered with a single table or solely by joins.  You’ll often find you need to use joins in conjunction with group by statements. Always write the raw query first and then look at the results. Next, you have to figure out the best way to group them, rewrite your select clause and add a group by clause in the end.

Digging Through Data
I find this is the most lacking skill in many programmers. In fact, many otherwise-talented programmers holding Master’s Degrees fail to get jobs because they couldn’t analyze rows of data objectively during interviews. It’s just something that’s not taught but is crucial to get under you belt. Why? Eventually, some query is not going to perform as you may expect. And, the only way to find discrepancies is to look at rows of data, identify what join isn’t finding a match or where bad data is throwing things into chaos. Get familiar with how joins actually work, even if you have to manually walk through the logic of a large stored procedure’s tree of joins. It’s boring and time-consuming but absolutely necessary.

Take the time to master the core skills that will make you a successful SQL Programmer and avoid queries that run for five hours!

Studying a functional programming language is a good way to discover new approaches to problems and different ways of thinking. Although functional programming has much in common with logic and imperative programming, it uses unique abstractions and a different toolset for solving problems. Likewise, many current mainstream languages are beginning to pick up and integrate various techniques and features from functional programming.

Many authorities feel that Haskell is a great introductory language for learning functional programming. However, there are various other possibilities, including Scheme, F#, Scala, Clojure, Erlang and others.

Haskell is widely recognized as a beautiful, concise and high-performing programming language. It is statically typed and supports various cool features that augment language expressivity, including currying and pattern matching. In addition to monads, the language support a type-class system based on methods; this enables higher encapsulation and abstraction. Advanced Haskell will require learning about combinators, lambda calculus and category theory. Haskell allows programmers to create extremely elegant solutions.

Scheme is another good learning language -- it has an extensive history in academia and a vast body of instructional documents. Based on the oldest functional language -- Lisp -- Scheme is actually very small and elegant. Studying Scheme will allow the programmer to master iteration and recursion, lambda functions and first-class functions, closures, and bottom-up design.

Supported by Microsoft and growing in popularity, F# is a multi-paradigm, functional-first programming language that derives from ML and incorporates features from numerous languages, including OCaml, Scala, Haskell and Erlang. F# is described as a functional language that also supports object-oriented and imperative techniques. It is a .NET family member. F# allows the programmer to create succinct, type-safe, expressive and efficient solutions. It excels at parallel I/O and parallel CPU programming, data-oriented programming, and algorithmic development.

Scala is a general-purpose programming and scripting language that is both functional and object-oriented. It has strong static types and supports numerous functional language techniques such as pattern matching, lazy evaluation, currying, algebraic types, immutability and tail recursion. Scala -- from "scalable language" -- enables coders to write extremely concise source code. The code is compiled into Java bytecode and executes on the ubiquitous JVM (Java virtual machine).

Like Scala, Clojure also runs on the Java virtual machine. Because it is based on Lisp, it treats code like data and supports macros. Clojure's immutability features and time-progression constructs enable the creation of robust multithreaded programs.

Erlang is a highly concurrent language and runtime. Initially created by Ericsson to enable real-time, fault-tolerant, distributed applications, Erlang code can be altered without halting the system. The language has a functional subset with single assignment, dynamic typing, and eager evaluation. Erlang has powerful explicit support for concurrent processes.

Computer Programming as a Career?

What little habits make you a better software engineer?

As much as we love to assume free Wi-Fi is secure, this is far from the truth. Because you are attaching to a service many others are connected to as well, without security measures, your device can be hacked, especially if the network is unencrypted. Because this encryption involves handing out a 26-character hexadecimal key to every individual wanting to use that network, most places opt for ease of access over security. And even with a secure network, your information is vulnerable to everyone else who has the password and is on the network.

This may not seem like such a big deal and many people don’t believe they have anything to hide on their personal devices, but remember what you use on those devices. Chances are your e-mail is attached as well as all other social media sites. You may have apps that track your finances or private messages to certain others that you would never want anyone else to see. Luckily, there are steps that can be taken to reduce and prevent any unwanted information grabbers from accessing your personal information.

To start, go through your computer’s settings in order to verify your operating system’s security functions are all set to offer the highest protection. Open up the Control Panel and double check that your Firewall is enabled for both private and public networks. Then, go to Network and Sharing to open Change advanced sharing settings. In here, you can turn off file and printer sharing and network discovery for public networks.

One of the most important things to watch for is HTTPS. Hypertext Transfer Protocol Secure ensures secure communication across the web. Many of the major email systems use this when you log in (as another layer of password protection) but drop the security as soon as the login is complete. To keep this going, HTTPS Everywhere is a browser extension that gives you a secure connection when browsing some of the more popular sites. It can also be programmed for other sites you like to visit that don’t use HTTPS.

Not every place on the internet provides the choice of HTTPS, and VPNs are there to fill in the security gap. Virtual Private Networks allows data to be sent and received through public access points as if it were directly connected to a secure network. Many businesses offer this for company devices, but if you are an individual looking for that kind of security, ProXPN is a free version that can be upgraded. Unfortunately, it limits your speed, but other choices include VPNBook, OpenVPN Shield Exchange, and OkayFreedom.

With these three steps implemented, secure public Wi-Fi can be achieved. No longer will you have to worry about connecting in an unsure environment with strangers, never knowing if your information is being stolen. With all of the options free of charge, it is also an affordable means of protecting yourself that only takes a little time and effort to implement and guarantee safety.

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Password Management Tools

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What are a few unique pieces of career advice that nobody ever mentions?