Manipulating transitions and contexts

Getting a transition or context from a transition id

REVEN v2.2.0 
tr = server.trace.transition(1234)
ctx_before = server.trace.context_before(1234)
ctx_after = server.trace.context_after(1234)

Context <-> Transition

Transition -> Context

REVEN v2.2.0 
ctx_before = tr.context_before()
ctx_after = tr.context_after()

Context -> Transition

REVEN v2.6.0 
if ctx != server.trace.first_context:
    tr_before = ctx.transition_before()
if ctx != server.trace.last_context:
    tr_after = ctx.transition_after()
REVEN v2.2.0 
if ctx != server.trace.context_before(0):
    tr_before = ctx.transition_before()
if ctx != server.trace.context_after(server.trace.transition_count - 1):
    tr_after = ctx.transition_after()
There are not always transitions around a context

While transition.context_before/context_after() always works, one must handle the case where a context is the first/last of the trace, in which case no transition before/after it can be accessed.

Trying to access the transition before the first context/after the last, will trigger an IndexError.

Getting the next/previous context and transition

next_tr = tr + 1
prev_tr = tr - 1
next_ctx = ctx + 1
prev_ctx = ctx - 1
next_next_tr = tr + 2
# ...
There is not always a next/previous transition/context

Make sure that the resulting transition/context is in range when adding/subtracting an offset to generate a new transition/context.

Trying to access a transition/context out-of-range will trigger an IndexError.

Iterating on a range of transitions/contexts

REVEN v2.2.0 
for tr in server.trace.transitions(0, 1000):
    print(tr)

for ctx in server.trace.contexts():
    print(ctx)

Getting the first/last context/transition in the trace

REVEN v2.6.0 
first_tr = server.trace.first_transition
last_tr = server.trace.last_transition
first_ctx = server.trace.first_context
last_ctx = server.trace.last_context
REVEN v2.2.0 
first_tr = server.trace.transition(0)
last_tr = server.trace.transition(server.trace.transition_count - 1)
first_ctx = server.trace.context_before(0)
last_ctx = server.trace.context_after(server.trace.transition_count - 1)