docs: about writing custom objects

docs/reference/Dataclasses.md

@@ -42,3 +42,10 @@ valid.
 
 ::: osmium.osm.Box
 ::: osmium.osm.Location
+
+## Mutable OSM objects
+
+::: osmium.osm.mutable.OSMObject
+::: osmium.osm.mutable.Node
+::: osmium.osm.mutable.Way
+::: osmium.osm.mutable.Relation

docs/user_manual/06-Writing-Data.md

@@ -69,6 +69,59 @@ You can also write data that is not based on OSM input data at all. The write
 functions will accept any Python object that mimics the attributes of a
 node, way or relation.
 
+Here is a simple example that writes out four random points:
+
+!!! example
+    ``` python
+    from random import uniform
+
+    class RandomNode:
+        def __init__(self, name, id):
+            self.id = id
+            self.location = (uniform(-180, 180), uniform(-90, 90))
+            self.tags = {'name': name}
+
+    with osmium.SimpleWriter('points.opl') as writer:
+        for i in range(4):
+            writer.add_node(RandomNode(f"Random {i}", i))
+    ```
+
+The following table gives an overview over the recognised attributes and
+acceptable types. If an attribute is missing, then pyosmium will choose a
+suitable default or leave the attribute out completely from the output if
+that is possible.
+
+| attribute | types |
+|-----------|----------------------------|
+| id        | `int` |
+| version   | `int` (positive non-zero value) |
+| visible   | `bool` |
+| changeset | `int` (positive non-zero value) |
+| timestamp | `str` or `datetime` (will be translated to UTC first) |
+| uid       | `int` |
+| tags      | [osmium.osm.TagList][], a dict-like object or a list of tuples, where each tuple contains a (key, value) string pair |
+| user      | `str` |
+| location  | _(node only)_ [osmium.osm.Location][] or a tuple of lon/lat coordinates |
+| nodes     | _(way only)_ [osmium.osm.NodeRefList][] or a list consisting of either [osmium.osm.NodeRef][]s or simple node ids |
+| members   | _(relation only)_ [osmium.osm.RelationMemberList][] or a list consisting of either [osmium.osm.RelationMember][]s or tuples of `(type, id, role)`. The member type must be a single character 'n', 'w' or 'r'. |
+
+The `osmium.osm.mutable` module offers pure Python-object versions of `Node`,
+`Way` and `Relation` to make the creation of custom objects easier. Any of
+the allowable attributes may be set in the constructor. This makes the
+example for writing random points a bit shorter:
+
+!!! example
+    ``` python
+    from random import uniform
+
+    with osmium.SimpleWriter('points.opl') as writer:
+        for i in range(4):
+            writer.add_node(osmium.osm.mutable.Node(
+                id=i, location = (uniform(-180, 180), uniform(-90, 90)),
+                tags={'name': f"Random {i}"}))
+    ```
+
+
 ## Writer types
 
 pyosmium implements three different writer classes: the basic

src/osmium/osm/mutable.py

@@ -19,21 +19,23 @@
                        Sequence[Union[osmium.osm.RelationMember, Tuple[str, int, str]]]]
 
 class OSMObject:
-    """Mutable version of ``osmium.osm.OSMObject``. It exposes the following
-       attributes ``id``, ``version``, ``visible``, ``changeset``, ``timestamp``,
-       ``uid`` and ``tags``. Timestamps may be strings or datetime objects.
-       Tags can be an osmium.osm.TagList, a dict-like object
-       or a list of tuples, where each tuple contains a (key value) string pair.
-
-       If the ``base`` parameter is given in the constructor, then the object
-       will be initialised first from the attributes of this base object.
+    """ Mutable version of [osmium.osm.OSMObject][].
     """
 
     def __init__(self, base: Optional['OSMObjectLike'] = None,
                  id: Optional[int] = None, version: Optional[int] = None,
                  visible: Optional[bool] = None, changeset: Optional[int] = None,
                  timestamp: Optional[datetime] = None, uid: Optional[int] = None,
                  tags: Optional['TagSequence'] = None, user: Optional[str] = None) -> None:
+        """ Initialise an object with the following optional
+            attributes: `id`, `version`, `visible`, `changeset`, `timestamp`,
+            `uid` and `tags`. Timestamps may be strings or datetime objects.
+            Tags can be an osmium.osm.TagList, a dict-like object
+            or a list of tuples, where each tuple contains a (key value) string pair.
+
+            If the `base` parameter is given in the constructor, then the object
+            will be initialised first from the attributes of this base object.
+        """
         if base is None:
             self.id = id
             self.version = version
@@ -55,14 +57,18 @@ def __init__(self, base: Optional['OSMObjectLike'] = None,
 
 
 class Node(OSMObject):
-    """The mutable version of ``osmium.osm.Node``. It inherits all attributes
-       from osmium.osm.mutable.OSMObject and adds a `location` attribute. This
-       may either be an `osmium.osm.Location` or a tuple of lon/lat coordinates.
+    """ The mutable version of [osmium.osm.Node][].
     """
 
     def __init__(self, base: Optional[Union['Node', 'osmium.osm.Node']] = None,
                  location: Optional['LocationLike'] = None,
                  **attrs: Any) -> None:
+        """ Initialise a node with all optional attributes
+            from osmium.osm.mutable.OSMObject as well as a `location` attribute.
+            This may either be an [osmium.osm.Location][] or a tuple of
+            lon/lat coordinates.
+
+        """
         OSMObject.__init__(self, base=base, **attrs)
         if base is None:
             self.location = location
@@ -71,30 +77,35 @@ def __init__(self, base: Optional[Union['Node', 'osmium.osm.Node']] = None,
 
 
 class Way(OSMObject):
-    """The mutable version of ``osmium.osm.Way``. It inherits all attributes
-       from osmium.osm.mutable.OSMObject and adds a `nodes` attribute. This may
-       either be and ``osmium.osm.NodeList`` or a list consisting of
-       ``osmium.osm.NodeRef`` or simple node ids.
+    """ The mutable version of [osmium.osm.Way][].
     """
 
     def __init__(self, base: Optional[Union['Way', 'osmium.osm.Way']] = None,
                  nodes: Optional['NodeSequence'] = None, **attrs: Any) -> None:
+        """ Initialise a way with all optional attributes
+            from osmium.osm.mutable.OSMObject as well as a `nodes` attribute.
+            This may either be an [osmium.osm.NodeRefList][] or a list
+            consisting of [osmium.osm.NodeRef][] or simple node ids.
+        """
         OSMObject.__init__(self, base=base, **attrs)
         if base is None:
             self.nodes = nodes
         else:
             self.nodes = nodes if nodes is not None else base.nodes
 
 class Relation(OSMObject):
-    """The mutable version of ``osmium.osm.Relation``. It inherits all attributes
-       from osmium.osm.mutable.OSMObject and adds a `members` attribute. This
-       may either be an ``osmium.osm.RelationMemberList`` or a list consisting
-       of ``osmium.osm.RelationMember`` or tuples of (type, id, role). The
-       member type should be a single character 'n', 'w' or 'r'.
+    """ The mutable version of [osmium.osm.Relation][].
     """
 
     def __init__(self, base: Optional[Union['Relation', 'osmium.osm.Relation']] = None,
                  members: Optional['MemberSequence'] = None, **attrs: Any) -> None:
+        """ Initialise a relation with all optional attributes
+            from osmium.osm.mutable.OSMObject as well as a `members` attribute.
+            This may either be an [osmium.osm.RelationMemberList][] or
+            a list consisting of [osmium.osm.RelationMember][] or
+            tuples of (type, id, role). The
+            member type must be a single character 'n', 'w' or 'r'.
+        """
         OSMObject.__init__(self, base=base, **attrs)
         if base is None:
             self.members = members

test/test_writer.py

@@ -5,6 +5,7 @@
 # Copyright (C) 2022 Sarah Hoffmann.
 from contextlib import contextmanager
 from collections import OrderedDict
+from datetime import datetime, timezone, timedelta
 import uuid
 
 import pytest
@@ -54,6 +55,7 @@ def __init__(self, **params):
       (O(uid=987), '0 v0 dV c0 t i987 u T'),
       (O(timestamp='2012-04-14T20:58:35Z'), '0 v0 dV c0 t2012-04-14T20:58:35Z i0 u T'),
       (O(timestamp=mkdate(2009, 4, 14, 20, 58, 35)), '0 v0 dV c0 t2009-04-14T20:58:35Z i0 u T'),
+      (O(timestamp=datetime(2009, 4, 14, 20, 58, 35, tzinfo=timezone(timedelta(hours=1)))), '0 v0 dV c0 t2009-04-14T19:58:35Z i0 u T'),
       (O(timestamp='1970-01-01T00:00:01Z'), '0 v0 dV c0 t1970-01-01T00:00:01Z i0 u T')
     ])
 class TestWriteAttributes: