Editing IfcOpenShell code examples

{{Template:Start coding}}
{{Template:IfcOpenShell}}
Before getting started, you may be interested in [[Using the Python console with BlenderBIM Add-on]], to quickly install all the software and development environment you need for writing and running code, without any administrator privileges required. You may also find it useful watching [https://www.youtube.com/watch?v=WZPNaAM9ZuQ this video] which is complementary.

=Crash course=

To load a file, you'll need to import IfcOpenShell and store the IFC file in a variable. We'll use the variable <code>ifc</code>. The <code>ifc</code> will be then used throughout.

<syntaxhighlight lang="python">
import ifcopenshell
ifc = ifcopenshell.open('/path/to/your/file.ifc')
</syntaxhighlight>

...or if you already opened the file in BlenderBIM, for example, you could use...

<syntaxhighlight lang="python">
import ifcopenshell
from blenderbim.bim.ifc import IfcStore
ifc = ifcopenshell.open(IfcStore.path)
</syntaxhighlight>

Let's see what IFC schema we are using:

<syntaxhighlight lang="python">
print(ifc.schema) # May return IFC2X3 or IFC4
</syntaxhighlight>

Let's get the first piece of data in our IFC file:

<syntaxhighlight lang="python">
print(ifc.by_id(1))
</syntaxhighlight>

But getting data from beginning to end isn't too meaningful to humans. What if we knew a <code>GlobalId</code> value instead?

<syntaxhighlight lang="python">
print(ifc.by_guid('0EI0MSHbX9gg8Fxwar7lL8'))
</syntaxhighlight>

If we're not looking specifically for a single element, perhaps let's see how many walls are in our file, and count them:

<syntaxhighlight lang="python">
walls = ifc.by_type('IfcWall')
print(len(walls))
</syntaxhighlight>

Once we have an element, we can see what IFC class it is:

<syntaxhighlight lang="python">
wall = ifc.by_type('IfcWall')[0]
print(wall.is_a()) # Returns 'IfcWall'
</syntaxhighlight>

You can also test if it is a certain class, as well as check for parent classes too:

<syntaxhighlight lang="python">
print(wall.is_a('IfcWall')) # Returns True
print(wall.is_a('IfcElement')) # Returns True
print(wall.is_a('IfcWindow')) # Returns False
</syntaxhighlight>

Let's quickly check the STEP ID of our element:

<syntaxhighlight lang="python">
print(wall.id())
</syntaxhighlight>

Let's get some attributes of an element. IFC attributes have a particular order. We can access it just like a list, so let's get the first and third attribute:

<syntaxhighlight lang="python">
print(wall[0]) # The first attribute is the GlobalId
print(wall[2]) # The third attribute is the Name
</syntaxhighlight>

Knowing the order of attributes is boring and technical. We can access them by name too:

<syntaxhighlight lang="python">
print(wall.GlobalId)
print(wall.Name)
</syntaxhighlight>

Getting attributes one by one is tedious. Let's grab them all:

<syntaxhighlight lang="python">
print(wall.get_info()) # Gives us a dictionary of attributes, such as {'id': 8, 'type': 'IfcWall', 'GlobalId': '2_qMTAIHrEYu0vYcqK8cBX', ... }
</syntaxhighlight>

Let's see all the properties and quantities associated with this wall:

<syntaxhighlight lang="python">
import ifcopenshell.util
import ifcopenshell.util.element
print(ifcopenshell.util.element.get_psets(wall))
</syntaxhighlight>

Some attributes are special, called "inverse attributes". They happen when another element is referencing our element. They can reference it for many reasons, like to define a relationship, such as if they create a void in our wall, join our wall, or define a quantity take-off value for our wall, among others. Just treat them like regular attributes:

<syntaxhighlight lang="python">
print(wall.IsDefinedBy)
</syntaxhighlight>

Perhaps we want to see all elements which are referencing our wall?

<syntaxhighlight lang="python">
print(ifc.get_inverse(wall))
</syntaxhighlight>

Let's do the opposite, let's see all the elements which our wall references instead:

<syntaxhighlight lang="python">
print(ifc.traverse(wall))
print(ifc.traverse(wall, max_levels=1)) # Or, let's just go down one level deep
</syntaxhighlight>

If you want to modify data, just assign it to the relevant attribute:

<syntaxhighlight lang="python">
wall.Name = 'My new wall name'
</syntaxhighlight>

You can also generate new <code>GlobalId</code>s:

<syntaxhighlight lang="python">
wall.GlobalId = ifcopenshell.guid.new()
</syntaxhighlight>

After modifying some IFC data, you can save it to a new IFC-SPF file:

<syntaxhighlight lang="python">
ifc.write('/path/to/a/new.ifc')
</syntaxhighlight>

You can generate a new IFC from scratch too, instead of reading an existing one:

<syntaxhighlight lang="python">
ifc = ifcopenshell.file()
# Or if you want a particular schema:
ifc = ifcopenshell.file(schema='IFC4')
</syntaxhighlight>

You can create new IFC elements, and add it either to an existing or newly created IFC file object:

<syntaxhighlight lang="python">
new_wall = ifc.createIfcWall() # Will return #1=IfcWall($,$,$,$,$,$,$,$,$) - notice all of the attributes are blank!
print(ifc.by_type('IfcWall')) # Will return a list with our wall in it: [#1=IfcWall($,$,$,$,$,$,$,$,$)]
</syntaxhighlight>

Alternatively, you can also use this way to create new elements:

<syntaxhighlight lang="python">
ifc.create_entity('IfcWall')
</syntaxhighlight>

Specifying more arguments lets you fill in attributes while creating the element instead of assigning them separately. You specify them in the order of the attributes.

<syntaxhighlight lang="python">
ifc.create_entity('IfcWall', ifcopenshell.guid.new()) # Gives us #1=IfcWall('0EI0MSHbX9gg8Fxwar7lL8',$,$,$,$,$,$,$,$)
</syntaxhighlight>

Again, knowing the order of attributes is difficult, so you can use keyword arguments instead:

<syntaxhighlight lang="python">
ifc.create_entity('IfcWall', GlobalId=ifcopenshell.guid.new(), Name='Wall Name') # Gives us #1=IfcWall('0EI0MSHbX9gg8Fxwar7lL8',$,'Wall Name',$,$,$,$,$,$)
</syntaxhighlight>

Sometimes, it's easier to expand a dictionary:

<syntaxhighlight lang="python">
data = {
    'GlobalId': ifcopenshell.guid.new(),
    'Name': 'Wall Name'
}
ifc.create_entity('IfcWall', **data)
</syntaxhighlight>

Some attributes of an element aren't just text, they may be a reference to another element. Easy:

<syntaxhighlight lang="python">
wall = ifc.createIfcWall()
wall.OwnerHistory = ifc.createIfcOwnerHistory()
</syntaxhighlight>

What if we already have an element from one IFC file and want to add it to another?

<syntaxhighlight lang="python">
wall = ifc.by_type('IfcWall')[0]
new_ifc = ifcopenshell.file()
new_ifc.add(wall)
</syntaxhighlight>

Fed up with an object? Let's delete it:

<syntaxhighlight lang="python">
ifc.remove(wall)
</syntaxhighlight>

=Geometry processing=

The usage of IfcOpenShell for geometry processing is currently considered to be moderate to advanced. There are two approaches to processing geometry. One approach is to traverse the <code>Representation</code> attribute of the IFC element, and parse it yourself. This requires an in-depth understanding of IFC geometric representations, as well as its many caveats with units and transformations, but can be very simple to extract specific types of geometry. The second approach is to use IfcOpenShell's shape processing features, which will convert almost all IFC representations into a triangulated mesh. Regardless of the source format, once it is in a mesh representation, you may use standard mesh geometry processing algorithms to analyse the geometry. This makes it easier to write generic code for any representation, but may be harder to extract certain geometric features.

Note: this article is a work in progress.

TODO: talk about [https://github.com/IfcOpenShell/IfcOpenShell/issues/866 naming in ids].

<syntaxhighlight lang="python">
import multiprocessing
import ifcopenshell
import ifcopenshell.geom

try:
    ifc_file = ifcopenshell.open('/path/to/your/file.ifc')
except:
    print(ifcopenshell.get_log())
else:
    settings = ifcopenshell.geom.settings()
    iterator = ifcopenshell.geom.iterator(settings, ifc_file, multiprocessing.cpu_count())
    if iterator.initialize():
        while True:
            shape = iterator.get()
            element = ifc_file.by_guid(shape.guid)
            faces = shape.geometry.faces # Indices of vertices per triangle face e.g. [f1v1, f1v2, f1v3, f2v1, f2v2, f2v3, ...]
            verts = shape.geometry.verts # X Y Z of vertices in flattened list e.g. [v1x, v1y, v1z, v2x, v2y, v2z, ...]
            materials = shape.geometry.materials # Material names and colour style information that are relevant to this shape
            material_ids = shape.geometry.material_ids # Indices of material applied per triangle face e.g. [f1m, f2m, ...]

            # Since the lists are flattened, you may prefer to group them per face like so depending on your geometry kernel
            grouped_verts = [[verts[i], verts[i + 1], verts[i + 2]] for i in range(0, len(verts), 3)]
            grouped_faces = [[faces[i], faces[i + 1], faces[i + 2]] for i in range(0, len(faces), 3)]
            if not iterator.next():
                break
</syntaxhighlight>

==Geometry tree (clash detection/ray tracing etc…)==
You can use [[https://blenderbim.org/docs-python/ifcopenshell-python/geometry_tree.html geometry tree]] to perform various task like clash detection and ray tracing. Trees are common terms is geometry libraries. IfcOpenShell tree has [[https://en.wikipedia.org/wiki/Bounding_volume_hierarchy BVHTree]] functionalities.

=IFC Query Syntax=

Sometimes, you'd like to query an IFC file for a series of elements. It is possible to write this out manually, by means of functions like <code>by_type()</code> and <code>if</code> statements, and <code>for</code> loops. However, a shorthand query syntax has been invented that makes this process much easier. This is made available in the <code>ifcopenshell.util.selector</code> module.

In this simple example below, we use the <code>#</code> and <code>.</code> prefix to our query tells it that we want to search by IFC <code>GlobalId</code> and class type respectively. Whitespace is optional in queries, but is used in these examples for readability.

<syntaxhighlight lang="python">
import ifcopenshell.util
from ifcopenshell.util.selector import Selector

ifc = ifcopenshell.open('/path/to/your/file.ifc')
selector = Selector()
element = selector.parse(ifc, '#2MLFd4X2f0jRq28Dvww1Vm') # Equivalent to ifc.by_guid('2MLFd4X2f0jRq28Dvww1Vm')
walls = selector.parse(ifc, '.IfcWall') # This is equivalent to ifc.by_type('IfcWall')
</syntaxhighlight>

It is also possible to search by any attribute:

<syntaxhighlight lang="python">
# This is equivalent to searching by GlobalId
elements = selector.parse(ifc, '.IfcSlab[GlobalId = "2MLFd4X2f0jRq28Dvww1Vm"]')

# This finds all slabs with "Precast" (case-sensitive) in the Name
elements = selector.parse(ifc, '.IfcSlab[Name *= "Precast"]')

# This finds all slabs which have a quantified net volume greater than 10 units
elements = selector.parse(ifc, '.IfcSlab[Qto_SlabBaseQuantities.NetVolume > "10"]')

# This finds all walls which have a particular fire rating property
elements = selector.parse(ifc, '.IfcWall[Pset_WallCommon.FireRating = "2HR"]')
</syntaxhighlight>

You can also search by spatial containment using the <code>@</code> symbol, for example:

<syntaxhighlight lang="python">
# If 0ehnsYoIDA7wC8yu69IDjv is the GlobalId of an IfcBuildingStorey, this gets all of the elements in that storey.
elements = selector.parse(ifc, '@ #0ehnsYoIDA7wC8yu69IDjv')
</syntaxhighlight>

Or by type using the <code>*</code> symbol:

<syntaxhighlight lang="python">
# If 1uVUwUxTX9Jg1NHVw5KZhI is the GlobalId of an IfcTypeElement, this gets all of the elements of that type.
elements = selector.parse(ifc, '* #1uVUwUxTX9Jg1NHVw5KZhI')
</syntaxhighlight>

You can use <code>AND</code> and <code>OR</code> statements, using the <code>&</code> and <code>|</code> symbols respectively:

<syntaxhighlight lang="python">
# This gets all the 2HR fire rated walls in a particular building storey:
elements = selector.parse(ifc, '@ #0ehnsYoIDA7wC8yu69IDjv & .IfcWall[Pset_WallCommon.FireRating = "2HR"]')

# This is equivalent to walls = ifc.by_type('IfcWall') + ifc.by_type('IfcSlab'), i.e. all walls and slabs
elements = selector.parse(ifc, '.IfcWall | .IfcSlab')
</syntaxhighlight>

You can also use parenthesis to group queries and combine them:

<syntaxhighlight lang="python">
# This gets all walls and slabs in a particular building storey
elements = selector.parse(ifc, '@ #0ehnsYoIDA7wC8yu69IDjv & ( .IfcWall | .IfcSlab )')
</syntaxhighlight>

<syntaxhighlight lang="python">
# This gets all walls and slabs in a particular space (if IfcRelSpaceBoundary exist)
elements = selector.parse(ifc, '@@ .IfcSpace & ( .IfcWall | .IfcSlab )')
</syntaxhighlight>


You can also use query a specific element. It is what you do when using [[BlenderBIM_Add-on/BlenderBIM_IFCCSV | IfcCsv]] for example.

<syntaxhighlight lang="python">
# This gets all walls and slabs in a particular building storey
wall = selector.parse(ifc, '.IfcWall')[0]
wall_name = selector.get_element_value(wall, "Name")
wall_type_name = selector.get_element_value(wall, "type.Name")
wall_is_external = selector.get_element_value(wall, "Pset_WallCommon.IsExternal")
</syntaxhighlight>

=Exploring IFC schema=
Get Schema :
<syntaxhighlight lang="python">
import ifcopenshell
schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name("IFC4")
</syntaxhighlight>

Explore class attributes :
<syntaxhighlight lang="python">
>>> ifc_pipe = schema.declaration_by_name("IfcPipeSegment")
>>> ifc_pipe.all_attributes()
(<attribute GlobalId: <type IfcGloballyUniqueId: <string>>>,
 <attribute OwnerHistory?: <entity IfcOwnerHistory>>,
 <attribute Name?: <type IfcLabel: <string>>>,
 <attribute Description?: <type IfcText: <string>>>,
 <attribute ObjectType?: <type IfcLabel: <string>>>,
 <attribute ObjectPlacement?: <entity IfcObjectPlacement>>,
 <attribute Representation?: <entity IfcProductRepresentation>>,
 <attribute Tag?: <type IfcIdentifier: <string>>>,
 <attribute PredefinedType?: <enumeration IfcPipeSegmentTypeEnum: (CULVERT, FLEXIBLESEGMENT, GUTTER, NOTDEFINED, RIGIDSEGMENT, SPOOL, USERDEFINED)>>)

>>> ifc_pipe.attribute_count()
9

>>> ifc_pipe.attribute_by_index(0)
<attribute GlobalId: <type IfcGloballyUniqueId: <string>>>

>>> ifc_pipe.attribute_index("Description")
3

>>> predefined_type = ifc_pipe.attribute_by_index(8)
>>> predefined_type.name()
'PredefinedType'

>>> predefined_type.optional()
True

>>> predefined_type.type_of_attribute()
<enumeration IfcPipeSegmentTypeEnum: (CULVERT, FLEXIBLESEGMENT, GUTTER, NOTDEFINED, RIGIDSEGMENT, SPOOL, USERDEFINED)>

# from name you can then recursively explore how create an entity as described above
>>> predefined_type.type_of_attribute().declared_type().name()
'IfcPipeSegmentTypeEnum'
</syntaxhighlight>

Get supertype :
<syntaxhighlight lang="python">
>>> ifc_pipe.supertype()
<entity IfcFlowSegment>
</syntaxhighlight>

Another way to get a list of supertypes :
<!-- From discussion here: https://app.element.io/#/room/#OSArch:matrix.org/$LKrDGOp4OT3Qfbpl-Yj8QeUDG5mowS0YXrAKr0OBjts -->
<syntaxhighlight lang="python">
>>> import ifcopenshell
>>> s = ifcopenshell.ifcopenshell_wrapper.schema_by_name('IFC4')
>>> e = s.declaration_by_name('IfcWall')
>>> inheritance = []
>>> while e.supertype():
...     inheritance.append(e.supertype())
...     e = e.supertype()
... 
>>> inheritance
[<entity IfcBuildingElement>, <entity IfcElement>, <entity IfcProduct>, <entity IfcObject>, <entity IfcObjectDefinition>, <entity IfcRoot>]
</syntaxhighlight>


Get subtypes :
<syntaxhighlight lang="python">
>>> super_type = ifc_pipe.supertype()
>>> super_type.subtypes()
(<entity IfcCableCarrierSegment>,
 <entity IfcCableSegment>,
 <entity IfcDuctSegment>,
 <entity IfcPipeSegment>)
</syntaxhighlight>


=Property and quantity sets (Pset and Qto)=
First import util for psets and qtos and initialise main class with schema name:
<syntaxhighlight lang="python"> 
>>> import ifcopenshell.util.pset
>>> from ifcopenshell import util
>>> pset_qto = util.pset.PsetQto("IFC4")
</syntaxhighlight>

Get all applicable psets/qtos names for a certain class :
<syntaxhighlight lang="python"> 
>>> pset_qto.get_applicable_names("IfcMaterial")
['Pset_MaterialCombustion',
 'Pset_MaterialCommon',
 'Pset_MaterialConcrete',
 'Pset_MaterialEnergy',
 'Pset_MaterialFuel',
 'Pset_MaterialHygroscopic',
 'Pset_MaterialMechanical',
 'Pset_MaterialOptical',
 'Pset_MaterialSteel',
 'Pset_MaterialThermal',
 'Pset_MaterialWater',
 'Pset_MaterialWood',
 'Pset_MaterialWoodBasedBeam',
 'Pset_MaterialWoodBasedPanel']
</syntaxhighlight>

You can also get a list of all applicable pset/qto templates to get more information:
<syntaxhighlight lang="python"> 
>>> pset_qto.get_applicable("IfcMaterial")[0]
#22772=IfcPropertySetTemplate('3Eppg0qUmHuO00025QrE$V',$,'Pset_MaterialCommon','A set of general material properties.',.PSET_TYPEDRIVENOVERRIDE.,'IfcMaterial',(#22775,#22778,#22781))
</syntaxhighlight>

You can also retrieve a standard Pset by name:
<syntaxhighlight lang="python"> 
>>> pset_template = pset_qto.get_by_name("Pset_MaterialCommon")
>>> pset_template
#22772=IfcPropertySetTemplate('3Eppg0qUmHuO00025QrE$V',$,'Pset_MaterialCommon','A set of general material,'IfcMaterial',(#22775,#22778,#22781))
>>> pset_template.get_info()
{'id': 22772,
 'type': 'IfcPropertySetTemplate',
 'GlobalId': '3Eppg0qUmHuO00025QrE$V',
 'OwnerHistory': None,
 'Name': 'Pset_MaterialCommon',
 'Description': 'A set of general material properties.',
 'TemplateType': 'PSET_TYPEDRIVENOVERRIDE',
 'ApplicableEntity': 'IfcMaterial',
 'HasPropertyTemplates': (#22775=IfcSimplePropertyTemplate('3IOi60qUmHuO00025QrE$V',$,'MolecularWeight','Molecular weight of material (typically gas).',.P_SINGLEVALUE.,'IfcMolecularWeightMeasure','',$,$,$,$,.READWRITE.),
  #22778=IfcSimplePropertyTemplate('3OMAA0qUmHuO00025QrE$V',$,'Porosity','The void fraction of the total volume occupied by material (Vbr - Vnet)/Vbr.',.P_SINGLEVALUE.,'IfcNormalisedRatioMeasure','',$,$,$,$,.READWRITE.),
  #22781=IfcSimplePropertyTemplate('3TjUq0qUmHuO00025QrE$V',$,'MassDensity','Material mass density.',.P_SINGLEVALUE.,'IfcMassDensityMeasure','',$,$,$,$,.READWRITE.))}
</syntaxhighlight>

=File validation=
Ifcopenshell allows you to validate a file against its corresponding schema.
==From command line==
<syntaxhighlight lang="python">
python -m ifcopenshell.validate some_file.ifc
</syntaxhighlight>
On GNU/Linux you can store result in a json file:
<syntaxhighlight lang="bash">
python -m ifcopenshell.validate --json some_file.ifc >> json_output_path.json
</syntaxhighlight>

==Inside a script==
It looks similar to command line way but you need to provide a logger (standard logger or json_logger as below).
<syntaxhighlight lang="python">
import ifcopenshell
import ifcopenshell.validate

ifc_file = ifcopenshell.open("some_file.ifc")
json_logger = ifcopenshell.validate.json_logger()
ifcopenshell.validate.validate(ifc_file, json_logger)
json_logger.statements
</syntaxhighlight>
=Date and time in IFC=
Date and time conversion can be error prone. Fortunately IFC has chosen wide used definitions so standard python [https://docs.python.org/3/library/datetime.html datetime] and [https://docs.python.org/3/library/time.html time] modules have tools to handle most of them.
==IfcTimeStamp==
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifctimestamp.htm IfcTimeStamp] is the elapsed number of seconds since 1 January 1970, 00:00:00 UTC. See [https://en.wikipedia.org/wiki/Unix_time wikipedia] for more detailed explanations. It is typically used to record when you create or modify an IFC object. Warning while python output a float, IFC expect an integer.
<syntaxhighlight lang="python">
import time
# To store current time
>>>int(time.time())
1610829915
# To convert it to datetime (UTC+1 in this example)
>>> import datetime
>>> datetime.date.fromtimestamp(0)
datetime.date(1970, 1, 1, 1, 0)
>>> datetime.date.fromtimestamp(1610829915)
datetime.date(2021, 1, 16, 21, 45, 15)
</syntaxhighlight>

==IfcDateTime==
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifcdatetime.htm IfcDateTime] is stored in ISO 8601 format : YYYY-MM-DDThh:mm:ss
Convert back and forth :
<syntaxhighlight lang="python">
from datetime import datetime
>>> dt = datetime.fromisoformat("2021-01-16T21:45:15")
>>> dt
datetime.datetime(2021, 1, 16, 21, 45, 15)
>>> dt.isoformat()
'2021-01-16T21:45:15'
</syntaxhighlight>
==IfcDate==
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifcdate.htm IfcDate] is similar to IfcDateTime but without the time part : YYYY-MM-DD
You can use <code>datetime.date</code> instead of <code>datetime.datetime</code> the same way.
==IfcTime==
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifctime.htm IfcTime] is similar to IfcDateTime but without the date part : hh:mm:ss
You can use <code>datetime.time</code> instead of <code>datetime.datetime</code> the same way.
==IfcDuration==
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifcduration.htm IfcDuration] is used to store a time interval (eg. time to perform a task) in ISO 8601 format. There is apparently no ready to use standard python module to handle it. It can be handled using regular expressions. For format given as example in IFC documentation :
<syntaxhighlight lang="python">
>>> import re
>>> re.match("P(\d+)Y(\d+)M(\d+)DT(\d+)H(\d+)M(\d+)S", "P2Y10M15DT10H30M20S").groups()
('2', '10', '15', '10', '30', '20')
</syntaxhighlight>

To handle all available formatting options defined in [https://en.wikipedia.org/wiki/ISO_8601#Durations ISO 8601] a more complex regular expression is required like following.
[https://pythex.org/?regex=P(%3F%3A(%3FP%3Cyear%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)%5BY-%5D)%3F(%3F%3A(%3FP%3Cmonth%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)%5BM-%5D)%3F(%3F%3A(%3FP%3Cweek%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)W)%3F(%3F%3A(%3FP%3Cday%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)D%3F)%3F(%3F%3AT(%3F%3A(%3FP%3Chour%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)%5BH%3A%5D)%3F(%3F%3A(%3FP%3Cminute%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)%5BM%3A%5D)%3F(%3F%3A(%3FP%3Csecond%3E%5Cd%2B%3F%5B%2C%5C.%5D%3F%5Cd*)S%3F)%3F)%3F&test_string=P3Y6M4DT12H30M5S%0AP1M%0APT1M%0AP1DT12H%0AP0%2C5Y%0AP0.5Y%0APT36H%0AP1DT12H%0AP0003-06-04T12%3A30%3A05%0AP05Y%0AP0..5Y%0AP0%2C.5Y&ignorecase=0&multiline=0&dotall=0&verbose=0 You can test it on pythex].

<code>P(?:(?P<year>\d+?[,\.]?\d*)[Y-])?(?:(?P<month>\d+?[,\.]?\d*)[M-])?(?:(?P<week>\d+?[,\.]?\d*)W)?(?:(?P<day>\d+?[,\.]?\d*)D?)?(?:T(?:(?P<hour>\d+?[,\.]?\d*)[H:])?(?:(?P<minute>\d+?[,\.]?\d*)[M:])?(?:(?P<second>\d+?[,\.]?\d*)S?)?)?</code>

==IfcCalendarDate==
{{warning|Deprecated: IFC2X3 only}}
Similar to <code>IfcDate</code> but in a different format. It has 3 attribute for day, month and year.
<syntaxhighlight lang="python">
>>> from datetime import date
>>> import ifcopenshell
>>> ifc = ifcopenshell.file(schema="IFC2X3")
>>> ifc_date = ifc.createIfcCalendarDate(16, 1, 2021)
>>> py_date = date(ifc_date.YearComponent, ifc_date.MonthComponent, ifc_date.DayComponent)
>>> py_date
datetime.date(2021, 1, 16)
>>> ifc.createIfcCalendarDate(py_date.day, py_date.month, py_date.year)
#4=IfcCalendarDate(16,1,2021)
</syntaxhighlight>

=Samples from web=
{| class="wikitable"
!Subject
!Language
!Version
!Additional infos
|-
| [https://academy.ifcopenshell.org/posts/ifcopenshell-optimizer-tutorial/ Optimize IFC files]
| python
| 0.6.0-0d93633
|-
| [https://academy.ifcopenshell.org/posts/calculate-differences-of-ifc-files-with-hashing/ Calculate Differences of IFC files with Hashing]
| python
| 0.6.0-0d93633
|-
|[https://pythoncvc.net/?p=851 Understanding placements in IFC using IfcOpenShell and FreeCAD]
| python
| 0.6.0a1
| FreeCAD 0.18 git
|-
| [https://thinkmoult.com/using-ifcopenshell-parse-ifc-files-python.html Using IfcOpenShell to parse IFC files with Python]
| python
|-
| [https://pythoncvc.net/?p=839 Read geometry as Boundary Representation in FreeCAD]
| python
| 0.6.0a1
| FreeCAD 0.18 git
|-
| [https://pythoncvc.net/?p=822 Read IFC geometry as triangle meshes in FreeCAD]
| python
| 0.6.0a1
| FreeCAD 0.18 git
|-
| [https://academy.ifcopenshell.org/posts/using-ifcopenshell-and-c%2B%2B-to-generate-alignments-through-the-ifc-4x1-schema/ Using IfcOpenShell and C++ to generate Alignments through the IFC 4×1 schema]
| python/C++
|-
| [https://academy.ifcopenshell.org/posts/creating-a-simple-wall-with-property-set-and-quantity-information/ Creating a simple wall with property set and quantity information]
| python
|-
| [https://academy.ifcopenshell.org/posts/using-ifcopenshell-and-pythonocc-to-generate-cross-sections-directly-from-an-ifc-file/ Using IfcOpenshell and pythonOCC to generate cross sections directly from an IFC file]
| python
| <= 0.6 ?
| pythonOCC 0.16.0 ?
|-
|[https://academy.ifcopenshell.org/posts/using-the-parsing-functionality-of-ifcopenshell-interactively/ Using the parsing functionality of IfcOpenShell interactively]
| python
|-
|[https://academy.ifcopenshell.org/posts/using-ifcopenshell-and-pythonocc-to-construct-new-geometry/ Using IfcOpenShell and pythonOCC to construct new geometry]
| python
| <= 0.6
| pythonOCC 0.16.0
|-
| [https://github.com/IfcOpenShell/IfcOpenShell/tree/v0.6.0/src/examples Various ifc creation examples (little house, geometry etc…)]
| C++
|}

[[Category:IfcOpenShell]]