The 
sigma
 command is the generic command used to manipulate sigma systems. The syntax of this command follows the standard schema of 
command/subcommand/majorhandle/minorlabel
.
Sigma properties begin with an S_,
Pseudo sigma system labels first , last and random are special values, which select the first sigma system in the sigma system list, the last, or a random item.
This is the list of officially supported subcommands:
sigma append ehandle label ?property value?...
s.append({?property:value,?...})
s.append(?property,value,?...)
Standard data manipulation command for appending property data. It is explained in more detail in the section about setting property data.
sigma atoms ehandle label ?filterset? ?filtermode?
s.atoms(?filters=?,?mode=?)
Standard cross-referencing command to obtain the labels or references of the atoms in the σ system. This is explained in more detail in the section about object cross-references.
sigma bonds ehandle label ?filterset? ?filtermode?
s.bonds(?filters=?,?mode=?)
Standard cross-referencing command to obtain the labels or references of the bonds between the atoms associated with a σ system. This is explained in more detail in the section about object cross-references.
sigma create ehandle ?atom/atomlist?...
Sigma(eref,?aref/arefsequence/alabel?,...)
Sigma(aref,...)
Sigma.Create(eref,?aref/arefsequence/alabel?,...)
Sigma.Create(aref,...)
Define a new σ system from an atom set, which may be empty. A new system is always created, even if one with the same atoms already exists. Before the command is executed, the default π system set is automatically instantiated if it was not yet computed. Adding a new system invalidates properties which are sensitive to σ set changes.
The command returns the label or reference of the new σ system.
sigma defined ehandle label property
s.defined(property)
This command checks whether a property is defined for the σ system. This is explained in more detail in the section about property validity checking. Note that this is 
not
 a check for the presence of property data! The 
ens valid 
command is used for this purpose.
sigma delete ehandle ?label?...
sigma delete ehandle all
s.delete()
Sigma.Delete(eref,?sref/slabel/srefsequence?,...)
Sigma.Delete(sref,...)
Sigma.Delete(eref,“all”)
This command deletes specific or all σ systems from the ensemble. A sigma property invalidation event is generated and thus the command may indirectly change the ensemble data.
sigma dget ehandle label propertylist ?filterset? ?parameterdict?
s.dget(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the
 sigma get 
command. The difference between 
sigma get 
and
 sigma dget
 is that the latter does not attempt computation of property data, but rather initializes the property values to the default and returns that default if the data is not yet available. For data already present, 
sigma get 
and
 sigma dget
 are equivalent.
sigma exists ehandle label ?filterlist?
s.exists(?filters=?)
Sigma.Exists(eref,label,?filters=?)
Check whether this σ system exists. Optionally, a filter list can be supplied to check for the presence of specific features. The command returns 0 if the system does not exist, or fails the filter, and 1 in case of successful testing.
sigma expr ehandle label expression
s.expr(expression)
Compute a standard SQL -style property expression for the σ system. This is explained in detail in the chapter on property expressions.
sigma fill ehandle label ?property value?...
s.fill({property:value,...})
s.fill(?property,value?,...)
Standard data manipulation command for setting data, ignoring possible mismatches between the lengths of the lists of objects associated with the property and the value list. It is explained in more detail in the section about setting property data.
sigma filter ehandle label filterlist
s.filter(filters)
Check whether a σ system passes a filter list. The return value is boolean 1 for success and 0 for failure.
sigma get ehandle label propertylist ?filterset? ?parameterdict?
s.get(property=,?filters=?,?parameters=?)
s[property]
s.property
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
sigma groups ehandle label ?filterset? ?filtermode?
s.groups(?filters=?,?groups=?)
Standard cross-referencing command to obtain the labels or references of the groups the σ system overlaps with. This is explained in more detail in the section about object cross-references. An overlap between a σ system and a group is established when there are common atoms which are contained in both objects.
sigma groups $ehandle 1
sigma index ehandle label
s.index()
Get the index of the σ system. The index is the position in the σ set of the ensemble. The first position is index 0.
sigma index $ehandle 99
sigma jget ehandle label propertylist ?filterset? ?parameterdict?
s.jget(property=,?filters=?,?parameters=?)
This is a variant of 
sigma get
 which returns the result data as a 
JSON
 formatted string instead of 
Tcl
 or 
Python
 interpreter objects.
sigma jnew ehandle label propertylist ?filterset? ?parameterdict?
s.jnew(property=,?filters=?,?parameters=?)
This is a variant of 
sigma new
 which returns the result data as a 
JSON
 formatted string instead of 
Tcl
 or 
Python
 interpreter objects.
sigma jshow ehandle label propertylist ?filterset? ?parameterdict?
s.jshow(property=,?filters=?,?parameters=?)
This is a variant of 
sigma show
 which returns the result data as a 
JSON
 formatted string instead of 
Tcl
 or 
Python
 interpreter objects.
sigma local ehandle label propertylist ?filterset? ?parameterdict?
s.local(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading and recalculating object data. It is explained in more detail in the section about retrieving property data.
sigma mol ehandle label ?filterset? ?filtermode?
s.mol(?filters=?,?mode=?)
Standard cross-referencing command to obtain the label or reference of the molecule a σ system is part of. This is explained in more detail in the section about object cross-references.
sigma new ehandle label propertylist ?filterset? ?parameterdict?
s.new(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
The difference between
 sigma get 
and
 sigma new 
is that the latter forces the re-computation of the property data, regardless whether it is present and valid, or not.
sigma nget ehandle label propertylist ?filterset? ?parameterdict?
s.nget(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the 
sigma get 
command. The difference between 
sigma get 
and
 sigma nget
 is that the latter always returns numeric data, even if symbolic names for the values are available.
sigma pis ehandle label ?filterset? ?filtermode?
s.pis(?filter=?,?mode=?)
Standard cross-referencing command to obtain the labels or references of the π systems the σ system overlaps with. This is explained in more detail in the section about object cross-references.
Sigma.Ref(eref,identifier)
Python
 only method to get a σ reference. See 
sigma sigma 
command.
sigma rings ehandle label ?filterset? ?filtermode?
s.rings(?filters=?,?mode=?)
Standard cross-referencing command to obtain the labels or references of the rings the σ system is associated with. This is explained in more detail in the section about object cross-references. Rings which only partially overlap with the sigma system are included.
sigma ringsystems ehandle label ?filterset? ?filtermode?
s.ringsystems(?filters=?,?mode=?)
Standard cross-referencing command to obtain the labels or references of the ring systems the σ system overlaps with. This is explained in more detail in the section about object cross-references.
sigma set ehandle label ?property value?...
s.set(?property,value?,...)
s.set({property:value,...})
s.property = value
s[property] = value
Standard data manipulation command. It is explained in more detail in the section about setting property data.
sigma show ehandle label propertylist ?filterset? ?parameterdict?
s.show(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the 
sigma get 
command. The difference between 
sigma get 
and
 sigma show
 is that the latter does not attempt computation of property data, but raises an error if the data is not present and valid. For data already present, 
sigma get 
and
 sigma show
 are equivalent.
sigma sigma ehandle label
Sigma.Ref(eref,identifier)
Standard cross-referencing command to obtain the label or reference of the σ system as stored in property S_LABEL . This is explained in more detail in the section about object cross-references.
sigma sigma $ehandle #0
returns the label of the first σ system of the ensemble σ set.
sigma sqldget ehandle label propertylist ?filterset? ?parameterdict?
s.sqldget(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the 
sigma get 
command. The differences between 
sigma get 
and
 sigma sqldget 
are that the latter does not attempt computation of property data, but initializes the property value to the default and returns that default, if the data is not present and valid; and that the 
SQL
 command variant formats the data as 
SQL
 values rather than for 
Tcl
 or 
Python
 script processing.
sigma sqlget ehandle label propertylist ?filterset? ?parameterdict?
s.sqlget(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the 
sigma get 
command. The difference between 
sigma get 
and
 sigma sqlget 
is that the 
SQL
 command variant formats the data as 
SQL
 values rather than for 
Tcl
 or 
Python
 script processing.
sigma sqlnew ehandle label propertylist ?filterset? ?parameterdict?
s.sqlnew(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the
 sigma get 
command. The differences between 
sigma get 
and
 sigma sqlnew
 are that the latter forces re-computation of the property data, and that the 
SQL
 command variant formats the data as 
SQL
 values rather than for 
Tcl
 or 
Python
 script processing.
sigma sqlshow ehandle label propertylist ?filterset? ?parameterdict?
s.sqlshow(property=,?filters=?,?parameters=?)
Standard data manipulation command for reading object data. It is explained in more detail in the section about retrieving property data.
For examples, see the 
sigma get 
command. The differences between 
sigma get 
and
 sigma sqlshow 
are that the latter does not attempt computation of property data, but raises an error if the data is not present and valid, and that the 
SQL
 command variant formats the data as 
SQL
 values rather than for 
Tcl
 or 
Python
 script processing.
sigma subcommands
dir(Sigma)
Lists all subcommands of the 
sigma
 command. Note that this command does not require an ensemble handle, nor a sigma label.