'Uncategorized' Category

  • Cambridge city geospatial statistics

    February 17, 2014

    Using the Cambridge (Massachusetts) GIS data, we can compute some interesting geospatial statistics. Subway stations Using the address points (20844 points) and the subway stations data files, we can find out how many Cambridge addresses are in a certain radius of a Cambridge subway station. More particularly, we want to find the percentage of Cambridge […]

  • API to access the Cambridge city geospatial data

    December 28, 2013

    The city of Cambridge, MA made a large set of geospatial data publicly available. I uploaded the layers to the geospatial web service I have running on EC2. You can now access the Cambridge geospatial data easily using the Python client or the raw API. Here is a tutorial.

  • REST service + Python client to access geographic data

    November 12, 2013

    This post shows how we can query geographic data using a simple Python client pointing to a GIS web service: SnowFloat. The data file here is the Vermont towns geographic data file. Its name is “Boundary_BNDHASH_region_towns”. We first upload the data file to the web service. The web service here is a layer on top […]

  • Massachusetts Census 2010 Towns maps and statistics using Python

    September 10, 2013

    Using the Massachusetts Census 2010 Towns data source, we generated the following maps and statistics. The software used relies on technologies such as Python and PostGIS. Note: The data source has been generated and published by MassGIS. Population change We can see some towns in Cape Cod and Western Massachusetts not growing as fast (few […]

  • Python, Twitter statistics and the 2012 French presidential election

    August 29, 2012

    This post describes how Pytolab was designed to process Tweets related to the 2012 French presidential election, in real-time. This post also goes over some of the statistics computed over a period of 9 months. Note: I presented this project at EuroSciPy 2012: abstract. Architecture Statistics Architecture The posts are received from the Twitter streaming […]

  • Twitter sentiment analysis using Python and NLTK

    January 2, 2012

    This post describes the implementation of sentiment analysis of tweets using Python and the natural language toolkit NLTK. The post also describes the internals of NLTK related to this implementation. Background The purpose of the implementation is to be able to automatically classify a tweet as a positive or negative tweet sentiment wise. The classifier […]

  • Python dictionary implementation

    August 29, 2011

    This post describes how dictionaries are implemented in the Python language. Dictionaries are indexed by keys and they can be seen as associative arrays. Let’s add 3 key/value pairs to a dictionary: The values can be accessed this way: The key ‘d’ does not exist so a KeyError exception is raised. Hash tables Python dictionaries […]

  • Python string objects implementation

    June 19, 2011

    This article describes how string objects are managed by Python internally and how string search is done. PyStringObject structure New string object Sharing string objects String search PyStringObject structure A string object in Python is represented internally by the structure PyStringObject. “ob_shash” is the hash of the string if calculated. “ob_sval” contains the string of […]

  • Python integer objects implementation

    May 15, 2011

    This article describes how integer objects are managed by Python internally. An integer object in Python is represented internally by the structure PyIntObject. Its value is an attribute of type long. To avoid allocating a new integer object each time a new integer object is needed, Python allocates a block of free unused integer objects […]

  • Python and cryptography with pycrypto

    April 22, 2011

    We are going to talk about the toolkit pycrypto and how it can help us speed up development when cryptography is involved. Hash functions Encryption algorithms Public-key algorithms Hash functions A hash function takes a string and produces a fixed-length string based on the input. The output string is called the hash value. Ideal hash […]

 
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