Retrieve OSM changeset information (pyosmium)

Question

I would like to ask if there's an easy way to query OSM changesets' information like user, timestamp, comment and hashtags in that changeset. In particular I would like to retrieve all the user names of the users which modified an area saving their changesets with a particular hashtag (similarly to default hashtags in HOT projects https://tasks.hotosm.org/)

My idea is to download the OSM data relative to my area of interest (in this case a country, taken from https://osm-internal.download.geofabrik.de/africa/senegal-and-gambia.html#)

So what I did until now is to download the following files from GeoFabrik.de:

• senegal-and-gambia-latest-internal.osm.pbf

• senegal-and-gambia-internal.osh.pbf

And I tried to run the following code (taken from https://oslandia.com/en/?s=timeline+handler) using Python and pyosmium library:

import osmium as osm
import pandas as pd

class TimelineHandler(osm.SimpleHandler):
    def __init__(self):
        osm.SimpleHandler.__init__(self)
        self.elements = []

    def add_elements(self, e, elem_type):
        self.elements.append([elem_type,
                              e.id,
                              e.version,
                              e.visible,
                              pd.Timestamp(e.timestamp),
                              e.uid,
                              e.changeset]) #only changeset id

    def node(self, n):
        self.add_elements(n, 'node')

    def way(self, w):
        self.add_elements(w, 'way')

    def relation(self, r):
        self.add_elements(r, 'relation')

tlhandler = TimelineHandler()
tlhandler.apply_file("senegal-and-gambia-latest-internal.osm.pbf")
colnames = ['type', 'id', 'version', 'visible', 'ts', 'uid', 'chgset']
elements = pd.DataFrame(tlhandler.elements, columns=colnames)

This doesn't solve my problem as I'm searching for changesets' information and not OSM data itself.

Maybe I'm missing a snippet to be added in the handler similar to:

    ...

    def changeset(self, c):
        self.add_elements(c, 'changeset')

    ...

I tried to add this snippet, but the handler gives no result.

Actually I'm wondering if I'm missing something in the data structure of osm/osh .pbf files, something on pyosmium or if the changeset information I'm searching for is contained in such files.

If the task cannot be performed with pyosmium and GeoFabrik, how can I do such operation?

Answer 1

Changeset data is provided in a separate Changeset Dump: Latest Weekly Changesets (2.5 GB) on planet.openstreetmap.org (not aware of extracts).

Beside the database import tools mentioned in the Wiki, Osmium Tool can handle the changeset file, see Working with changesets (don't know about pyosmium).

Answer 2

Eventually this code answered exactly my question:

import osmium as osm
import pandas as pd

class ChangesetHandler(osm.SimpleHandler):
    def __init__(self):
        osm.SimpleHandler.__init__(self)
        self.elements = []

    def add_elements(self, e, elem_type):
        comment=e.tags.get("comment")
        if type(comment) is not type(None) and "TheHashtag" in comment: 
        self.elements.append([e.id, #changeset id
                              e.user]) #username not user id

    def changeset(self, r):
        self.add_elements(r, 'changeset')

tlhandler = ChangesetHandler()
tlhandler.apply_file("changesets-latest.osm")
colnames = ['id','user']
elements = pd.DataFrame(tlhandler.elements, columns=colnames)
users=elements.user.unique()
print("Found %d users\n"%len(users))
print(users)

This code returns a list of all the usernames of the users having commented their changeset with certain hashtag. For sake of simplicity I supposed users didn't change their usernames in this time, otherwise one can consider to call e.uid instead of e.user in the handler.