about me



< May 2010 >
2 3 4 5 6 7 8

past articles »

Click for San Francisco, California Forecast

San Francisco, USA


Python CSV reader is much faster than pickle

If you are considering to serialize a large amount of data to the disk, performance may become a concern to you. Python provides a serialization tool in the pickle module. There is also an optimized version called the cPickle. But how do they perform?

The data of concern to me is tabular data. In order to do a bake off, I have generated 50,000 records of sample data. The CSV representation is shown below:

seq, name, address, city, age, birthday
1000,John M. Doe,2147 Main St.,Middle Town 14,47,1985-05-15
1001,John N. Doe,2148 Main St.,Middle Town 15,48,1985-05-16
1002,John O. Doe,2149 Main St.,Middle Town 16,49,1985-05-17
1003,John P. Doe,2150 Main St.,Middle Town 17,50,1985-05-18
1004,John Q. Doe,2151 Main St.,Middle Town 18,51,1985-05-19
1005,John R. Doe,2152 Main St.,Middle Town 19,52,1985-05-20
1006,John S. Doe,2153 Main St.,Middle Town 20,53,1985-05-21
1007,John T. Doe,211 Main St.,Middle Town 21,1,1985-05-22

Naturally, CSV is a contender for storing tabular data. (Indeed the data source I'm working with is in CSV format.) The two pickle modules produce identical data output. In addition, Python 2.6 also provides a JSON module that do the similar task as pickle but outputs a standard text based format. I included it in the comparison below.

First observation, CSV output the most compact data at 3MB. Pickle output is 40% larger at 4.2MB. JSON is somewhere in between. The speed? CSV is the winner among them all.

Method Load Time (ms) File size (MB)
CSV 188 3
CSV int 289 3
cPickle 692 4.2
pickle 1,815 4.2
JSON 4,975 3.9

Note that CSV reader create data items as string. In the sample data, two out of the six columns are integer fields. In order to do an apple-to-apple comparison I have another test that do integer conversion after loading such that the data loaded is identical to pickle's. This impacted the performance somewhat. But it is still more than twice as fast as the faster cPickle module. The standard library's JSON's performance trailing far behind, making it unsuitable for anything performance intensive. FYI, unlike the other modules, JSON's output is in unicode.

The test is done by Python 2.6 on Windows XP machine with 2.33GHz Core2 CPU (Download source code).

2010.05.12 [, ] - comments



blog comments powered by Disqus

past articles »


BBC News


Afghanistan: 'We have won the war, America has lost', say Taliban (14 Apr 2021)


George Floyd death: Ex-officer Chauvin will not take the stand (15 Apr 2021)


US imposes sanctions on Russia over cyber-attacks (15 Apr 2021)


France urges citizens to leave Pakistan amid anti-French protests (15 Apr 2021)


Why are so many babies dying of Covid-19 in Brazil? (14 Apr 2021)


Torres Strait 8: Australian Islanders in landmark climate fight (14 Apr 2021)


Why Australia is in hysterics over a 'navy twerking' dance (15 Apr 2021)


William Amos: Canadian politician seen naked in work Zoom call (15 Apr 2021)


China 'can save .6 trillion by scrapping coal', report says (15 Apr 2021)


Texas students disciplined over 'slave trade game' (15 Apr 2021)

more »


SF Gate


It pays to search for top-quality auto shop (6 Feb 2021)


Fired Boeing CEO is now working with Bay Area tractor startup (14 Dec 2020)


PG&E bills to rise over per year on average to fund wildfire risk reduction (5 Dec 2020)


Nasdaq seeks more diversity on boards of companies listed on exchange (2 Dec 2020)


Elizabeth Holmes Prosecutors Say Texts Show Theranos Beset With Problems (24 Nov 2020)


Ship traffic, November 1 (30 Oct 2020)

more »

Site feed Updated: 2021-Apr-13 15:00