This list is my summary of Quora question What are the best Python 2.7 modules for data mining?

Basics:

• numpy – numerical library, numpy.scipy.org/
• scipy – Advanced math, signal processing, optimization, statistics,www.scipy.org/
• matplotlib, python plotting – Matplotlib, matplotlib.org

Machine Learning and Data Mining:

• MDP, a collection of supervised and unsupervised learning algorithms,pypi.python.org/pypi/MDP/2.4
• mlpy, Machine Learning Python, mlpy.sourceforge.net
• NetworkX, for graph analysis, networkx.lanl.gov/
• Orange, Data Mining Fruitful & Fun, biolab.si
• pandas, Python Data Analysis Library,pandas.pydata.org
• pybrain, pybrain.org
• scikits-learn – Classic machine learning algorithms – Provide simple an efficient solutions to learning problems, scikit-learn.org/stable/

Natural Language:

• NLTK, Natural Language Toolkit, nltk.org

For web scraping:

• Scrapy, An open source web scraping framework for Python scrapy.org
• urllib/urllib2

http://www.kdnuggets.com/2012/11/best-python-modules-for-data-mining.html