Arie Bregman

Linux And Stuff

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Python: check if two strings are permutations of each other

Another question I cover in a presentation I’m preparing for “Open University meets Open Source” meetups.

What is a Permutation?

Permutation is the action of rearranging objects, characters or symbols into different, unique sequences.

Each sequence is called ‘permutation’.

It’s common to see people mix permutation with combination, but those are two different things. Remember, combination doesn’t care about the order, while permutation does.

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Python: check if one string is a rotation of another string

Another question I cover in a presentation I’m preparing for “Open University meets Open Source” meetups.

The question

You have two strings, str1 and str2 and you need to return True if the first string is a rotation of the second string. Otherwise, return False.


“hello”,    “llohe” -> True. If we’ll rotate the second string twice, you’ll get ‘hello’.

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OpenFlow: Introduction

What is OpenFlow?

If we tried to explain what OpenFlow is, a possible definition would be: OpenFlow is a protocol for controlling and interacting with forwarding behaviors of switches. It allows us to dynamically control  the behavior of the switches in our network. Many SDN (software defined network) and Open Source projects use OpenFlow or support it as a plugin, such as OpenStack Neutron and OpenDaylight.

But It’s hard to grasp what it is, what it solves and how it works only using this brief description. In order to truly understand what is OpenFlow, we need to start from the beginning, before SDN era.

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Networking: Collection of videos and slides

Usually I don’t publish a post on every new project I create, but in this case I believe a lot of people can find it helpful in their learning process. So for the junior networking folks out there, or folks who just enjoy learning more about networking, you might want to take a look on the following page:

Computer Networking

Basically, it’s a collection of networking videos and slides on a variety of computer networking subjects (sdn, ovs, neutron, openflow, general networking concepts, etc.).

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Python: Working with RPMs

In this post I’ll cover:

  • Using the dnf module for querying for RPMs
  • Exctract RPM details with re module
  • Comparing RPM versions

The complete code is included at the end.

Query for RPMs

In this part I’ll show you how to use the DNF module in order to search for RPMs and extract information on them such as arch, version and name.

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