The python keyword global is used in a function to distinguish a local representation of a variable with the same name. 

glbvar = 0

def setglbvar():
    global glbvar # include this declaration so that updates to glbvar are NOT LOCAL to this function
    glbvar = 1

def printglbvar():
    print glbvar     # No need for global declaration to read value of globvar

setglbvar()
printglbvar()       # Prints 1

In programming, memory leaks are a common issue, and it occurs when a computer uses memory but does not give it back to the operating system. Experienced programmers have the ability to diagnose a leak based on the symptoms. Some believe every undesired increase in memory usage is a memory leak, but this is not an accurate representation of a leak. Certain leaks only run for a short time and are virtually undetectable.

Memory Leak Consequences

Applications that suffer severe memory leaks will eventually exceed the memory resulting in a severe slowdown or a termination of the application.

How to Protect Code from Memory Leaks?

Preventing memory leaks in the first place is more convenient than trying to locate the leak later. To do this, you can use defensive programming techniques such as smart pointers for C++.  A smart pointer is safer than a raw pointer because it provides augmented behavior that raw pointers do not have. This includes garbage collection and checking for nulls.

If you are going to use a raw pointer, avoid operations that are dangerous for specific contexts. This means pointer arithmetic and pointer copying. Smart pointers use a reference count for the object being referred to. Once the reference count reaches zero, the excess goes into garbage collection. The most commonly used smart pointer is shared_ptr from the TR1 extensions of the C++ standard library.

Static Analysis

The second approach to memory leaks is referred to as static analysis and attempts to detect errors in your source-code. CodeSonar is one of the effective tools for detection. It provides checkers for the Power of Ten coding rules, and it is especially competent at procedural analysis. However, some might find it lagging for bigger code bases.

How to Handle a Memory Leak

For some memory leaks, the only solution is to read through the code to find and correct the error. Another one of the common approaches to C++ is to use RAII, which an acronym for Resource Acquisition Is Initialization. This approach means associating scoped objects using the acquired resources, which automatically releases the resources when the objects are no longer within scope. RAII has the advantage of knowing when objects exist and when they do not. This gives it a distinct advantage over garbage collection. Regardless, RAII is not always recommended because some situations require ordinary pointers to manage raw memory and increase performance. Use it with caution.

The Most Serious Leaks

Urgency of a leak depends on the situation, and where the leak has occurred in the operating system. Additionally, it becomes more urgent if the leak occurs where the memory is limited such as in embedded systems and portable devices.

To protect code from memory leaks, people have to stay vigilant and avoid codes that could result in a leak. Memory leaks continue until someone turns the system off, which makes the memory available again, but the slow process of a leak can eventually prejudice a machine that normally runs correctly.

Related:

The Five Principles of Performance

In Demand IT Skills

 Unlike traditional online courses that charge a fee, limit enrollment and provide credit or certification, Moocs (massive open online courses) are usually free or low cost and can host hundreds of  thousands global participants.  Although MOOC have been around for years in the form of collective techie learning gatherings, participation in 2012 has ballooned at a rapid pace likened to FaceBook in its heyday.  According to The Year of the MOOCarticle in the New YorkTimes, edX, a nonprofit start-up backed by Harvard and MIT, had 370,000 registrants in the fall of its first official courses. This paled in comparison to the amount of students that Courseraattained in its first year of online learning opportunities, 1.7 million!

Will MOOCs Replace education as we know it?

Like any new trend, massive participation in online classes has its challenges. Lynda Weinman has ample experience when pointing out that they are by no means a replacement for formal education.  As a former digital animator, special effects designer and classroom college teacher, Linda paved the path for an earlier version of MOOC education in the mid 90’s when she founded Lynda.comas an aide to her own students. Over four million students and 2,200 courses later she’s confident when clarifying that many of the collegespartnered with Lynda.com use the tutorials as added features to their existing courses.  When asked in an interview with ReadWriteBuilders, if high technical companies look at online programs in terms of advancement as a supplement to traditional education or as a way for people to further their careers, Lynda feels that “it’sjust one example of something that you can do to enhance your attractiveness to potential employers. But [it’s also important to have] a portfolio and body of work, references that actually work out, showing that you had success in the past.”

MOOC Benefits:

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

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