本文整理汇总了Python中sage.graphs.all.DiGraph.has_loops方法的典型用法代码示例。如果您正苦于以下问题：Python DiGraph.has_loops方法的具体用法？Python DiGraph.has_loops怎么用？Python DiGraph.has_loops使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类sage.graphs.all.DiGraph的用法示例。
在下文中一共展示了DiGraph.has_loops方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: _is_valid_digraph_edge_set
# 需要导入模块: from sage.graphs.all import DiGraph [as 别名]
# 或者: from sage.graphs.all.DiGraph import has_loops [as 别名]
def _is_valid_digraph_edge_set( edges, frozen=0 ):
"""
Returns True if the input data is the edge set of a digraph for a quiver (no loops, no 2-cycles, edge-labels of the specified format), and returns False otherwise.
INPUT:
- ``frozen`` -- (integer; default:0) The number of frozen vertices.
EXAMPLES::
sage: from sage.combinat.cluster_algebra_quiver.mutation_class import _is_valid_digraph_edge_set
sage: _is_valid_digraph_edge_set( [[0,1,'a'],[2,3,(1,-1)]] )
The given digraph has edge labels which are not integral or integral 2-tuples.
False
sage: _is_valid_digraph_edge_set( [[0,1],[2,3,(1,-1)]] )
True
sage: _is_valid_digraph_edge_set( [[0,1,'a'],[2,3,(1,-1)],[3,2,(1,-1)]] )
The given digraph or edge list contains oriented 2-cycles.
False
"""
try:
dg = DiGraph()
dg.allow_multiple_edges(True)
dg.add_edges( edges )
# checks if the digraph contains loops
if dg.has_loops():
print "The given digraph or edge list contains loops."
return False
# checks if the digraph contains oriented 2-cycles
if _has_two_cycles( dg ):
print "The given digraph or edge list contains oriented 2-cycles."
return False
# checks if all edge labels are 'None', positive integers or tuples of positive integers
if not all( i == None or ( i in ZZ and i > 0 ) or ( type(i) == tuple and len(i) == 2 and i[0] in ZZ and i[1] in ZZ ) for i in dg.edge_labels() ):
print "The given digraph has edge labels which are not integral or integral 2-tuples."
return False
# checks if all edge labels for multiple edges are 'None' or positive integers
if dg.has_multiple_edges():
for e in set( dg.multiple_edges(labels=False) ):
if not all( i == None or ( i in ZZ and i > 0 ) for i in dg.edge_label( e[0], e[1] ) ):
print "The given digraph or edge list contains multiple edges with non-integral labels."
return False
n = dg.order() - frozen
if n < 0:
print "The number of frozen variables is larger than the number of vertices."
return False
if [ e for e in dg.edges(labels=False) if e[0] >= n] <> []:
print "The given digraph or edge list contains edges within the frozen vertices."
return False
return True
except StandardError:
print "Could not even build a digraph from the input data."
return False