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(Financial Information eXchange) Protocol is a widely-used,
text-based protocol for interaction between parties in financial
trading. Banks, brokers, clearing firms, exchanges, and other general
market participants use FIX protocol for all phases of electronic
Typically, a FIX implementation exists as a FIX Engine: a standalone
service that acts as a gateway for other applications (matching
engines, trading algos, etc) and implements the FIX protocol. The
most popular Open Source FIX engine is probably one of the versions of
This package provides a simple implementation of the FIX application-layer protocol. It does no socket handling, and does not implement FIX recovery or any message persistence. It supports the creation, encoding, and decoding of FIX messages.
The module is licensed under the
MIT license <https://opensource.org/licenses/MIT>_.
While this is not legal advice, in short this means you're free to do
whatever you like with this code, with the exception of claiming you
Programmer's Guide <https://simplefix.readthedocs.io>_ for
To create a FIX message, first create an instance of the FixMessage class.
.. code-block:: python
msg = simplefix.FixMessage()
You can then add fields to the message as required. You should add the
standard header tags 8, 34, 35, 49, 52, and 56 to all messages. For most
append_pair() is the easiest way to add a field to the message.
When adding a UTCTimestamp value (ie, for tag 52) using
append_utc_timestamp() will take care of the formatting for you.
append_string() will decompose a "tag=value" string and add it as a proper
append_strings() will do the same for a sequence of "tag=value"
append_data() will correctly append a data field, setting the
length tag's value, and putting the value tag after the length in the
Once all fields are set, calling
encode() will return a byte buffer
containing the correctly formatted FIX message, with fields in the required
order, and automatically added and set values for the BodyLength (9) and
Checksum (10) fields.
Note that if you want to manually control the ordering of all fields, the
value of the BodyLength or Checksum fields, there's a 'raw' flag to the
encode() method that disables this functionality. This is useful for
creating known-bad messages for testing purposes.
To extract FIX messages from a byte buffer, such as that received from a
socket, you should first create an instance of the
FixParser class. For
each byte string received, append it to the internal reassembly buffer using
append_buffer() . At any time, you can call
get_message() : if there's
no complete message in the parser's internal buffer, it'll return None,
otherwise, it'll return a
Once you've received a
get_message() , you can: check
the number of fields with
count() , retrieve the value of a field using
get() or the built-in "[ ]" syntax, or iterate over all the fields using
"for ... in ...".
Members of repeating groups can be accessed using
get(tag, nth), where the
"nth" value is an integer indicating which occurrence of the tag to return
(note that the first occurrence is number one, not zero).
Comments, suggestions, bug reports, bug fixes -- all contributions to
this project are welcomed. See the project's
GitHub <https://github.com/da4089/simplefix>_ page for access to the latest
source code, and please open an
issue <https://github.com/da4089/simplefix/issues>_ for comments,
suggestions, and bugs.
See the CONTRIBUTING.rst file for more detailed instructions.
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