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Read, write and modify MARC bibliographic data

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pymarc is a python library for working with bibliographic data encoded in MARC21. It should work under python 2.x and 3.x. It provides an API for reading, writing and modifying MARC records. It was mostly designed to be an emergency eject seat, for getting your data assets out of MARC and into some kind of saner representation. However over the years it has been used to create and modify MARC records, since despite repeated calls for it to die as a format, MARC seems to be living quite happily as a zombie.

Below are some common examples of how you might want to use pymarc. If you run across an example that you think should be here please send a pull request.


Most often you will have some MARC data and will want to extract data from it. Here's an example of reading a batch of records and printing out the title. If you are curious this example uses the batch file available here in pymarc repository:

from pymarc import MARCReader
with open('test/marc.dat', 'rb') as fh:
    reader = MARCReader(fh)
    for record in reader:
The pragmatic programmer : from journeyman to master /
Programming Python /
Learning Python /
Python cookbook /
Python programming for the absolute beginner /
Web programming : techniques for integrating Python, Linux, Apache, and MySQL /
Python programming on Win32 /
Python programming : an introduction to computer science /
Python Web programming /
Core python programming /
Python and Tkinter programming /
Game programming with Python, Lua, and Ruby /
Python programming patterns /
Python programming with the Java class libraries : a tutorial for building Web
and Enterprise applications /
Learn to program using Python : a tutorial for hobbyists, self-starters, and all
who want to learn the art of computer programming /
Programming with Python /
BSD Sockets programming from a multi-language perspective /
Design patterns : elements of reusable object-oriented software /
Introduction to algorithms /
ANSI Common Lisp /

A pymarc.Record object has a few handy methods like title for getting at bits of a bibliographic record, others include: author, isbn, subjects, location, notes, physicaldescription, publisher, pubyear. But really, to work with MARC data you need to understand the numeric field tags and subfield codes that are used to designate various bits of information. There is a lot more hiding in a MARC record than these methods provide access to. For example the title method extracts the information from the 245 field, subfields a and b. You can access 245a like so:


Some fields like subjects can repeat. In cases like that you will want to use get_fields to get all of them as pmarc.Field objects, which you can then interact with further:

for f in record.get_fields('650'):

If you are new to MARC fields Understanding MARC is a pretty good primer, and the MARC 21 Formats page at the Library of Congress is a good reference once you understand the basics.


Here's an example of creating a record and writing it out to a file.

from pymarc import Record, Field
record = Record()
        tag = '245',
        indicators = ['0','1'],
        subfields = [
            'a', 'The pragmatic programmer : ',
            'b', 'from journeyman to master /',
            'c', 'Andrew Hunt, David Thomas.'
with open('file.dat', 'wb') as out:


Updating works the same way, you read it in, modify it, and then write it out again:

from pymarc import MARCReader
with open('test/marc.dat', 'rb') as fh:
    reader = MARCReader(fh)
    record = next(reader)
    record['245']['a'] = 'The Zombie Programmer'
with open('file.dat', 'wb') as out:


If you find yourself using MARC data a fair bit, and distributing it, you may make other developers a bit happier by using the JSON or XML serializations. pymarc has support for both. The main benefit here is that the UTF8 character encoding is used, rather than the frustratingly archaic MARC8 encoding. Also they will be able to use JSON and XML tools to get at the data they want instead of some crazy MARC processing library like, ahem, pymarc.


You'll probably just want to use pip to install pymarc:

pip install pymarc

If you'd like to download and install the latest source you'll need git:

git clone git://

You'll also need setuptools. Once you have the source and setuptools run the pymarc test suite to make sure things are in order with the distribution:

python test

And then install:

python install


The pymarc developers encourage you to join the pymarc Google Group if you need help. Also, please feel free to use issue tracking on Github to submit feature requests or bug reports. If you've got an itch to scratch, please scratch it, and send merge requests on Github.

If you start working with MARC you may feel like you need moral support in addition to technical support. The #code4lib channel on Freenode is a good place for both.


Copyright (c) 2005-2016 Gabriel Farrell, Mark Matienzo, Geoffrey Spear, Ed Summers



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