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Library to read/write the pcap-ng format used by various packet sniffers

Project description


Python library to parse the pcap-ng format used by newer versions of dumpcap & similar tools (wireshark, winpcap, …).


If you prefer the RTD theme, or want documentation for any version other than the latest, head here:

If you prefer the more comfortable, page-wide, default sphinx theme, a documentation mirror is hosted on GitHub pages:

CI build status

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Source code

Source, issue tracker etc. on GitHub:

Get the source from git:

git clone

Download zip of the latest version:

Install from pypi:

pip install python-pcapng

PyPI status

The official page on the Python Package Index is:

Latest PyPI version Number of PyPI downloads Supported Python versions Development Status License

Why this library?

  • I need to decently extract some information from a bunch of pcap-ng files, but apparently tcpdump has some problems reading those files,

    I couldn’t find other nice tools nor Python bindings to a library able to parse this format, so..

  • In general, it appears there are (quite a bunch of!) Python modules to parse the old (much simpler) format, but nothing for the new one.

  • And, they usually completely lack any form of documentation.

Isn’t it slow?

Yes, I guess it would be much slower than something written in C, but I’m much better at Python than C.

..and I need to get things done, and CPU time is not that expensive :)

(Maybe I’ll give a try porting the thing to Cython to speed it up, but anyways, pure-Python libraries are always useful, eg. for PyPy).

How do I use it?

Basic usage is as simple as:

from pcapng import FileScanner

with open('/tmp/mycapture.pcap', 'rb') as fp:
    scanner = FileScanner(fp)
    for block in scanner:
        pass  # do something with the block...

Have a look at the blocks documentation to see what they do; also, the examples directory contains some example scripts using the library.


Format specification is here:

Contributions are welcome, please contact me if you’re planning to do some big change, so that we can sort out the best way to integrate it.

Or even better, open an issue so the whole world can partecipate in the discussion :)

Pcap-ng write support

Support for writing pcap-ng files is “planned”; that means: I have some ideas on how to write that part and which would be the required changes to the library.

I didn’t add that part (yet) as I currently don’t need it, and I’m wondering whether anybody might (possible use cases are if you’re writing some packet capture tool in Python, or some other kind of capture-file manipulation thing).

If you need this feature, I’d like to hear from you (otherwise, I don’t really think I’m going to invest much time in something that no one needs..).



  • Support for “scanning” streams of pcap-ng data
  • Support for decoding the “standard” pcap-ng blocks:
    • Section headers
    • Interface description
    • Enhanced packet
    • Simple packet (deprecated)
    • Packet (deprecated)
    • Name resolution
    • Interface statistics

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