#to check to see if id exists in current folder:
myId = 'id to check for'

#in Script(Python) this will check current folder,
#as well as Acquired objects

if hasattr(context, myId): 
    return getattr(context, myId)

#another way is to use the default argument of getattr
return getattr(context, myId, 0)

#in a DTML Method you can
<dtml-if "_.hasattr(this(), myId )"> <dtml-var myId> exists
<dtml-else> doesnt exist
</dtml-if>

#or
<dtml-if "_.getattr(this(), myId, 0)"> <dtml-var myId> exists
<dtml-else> nope
</dtml-if>

#or simply
<dtml-if "myId in objectIds()"> in objectIds()
<dtml-else> not in objectIds()
</dtml-if>


#in a DTML Document
<dtml-if "_.getattr(this().aq_parent, myId, 0)"> <dtml-var myId> exists
<dtml-else> doesnt exist
</dtml-if>

#using objectIds
<dtml-if "myId in this().aq_parent.objectIds()"> in objectIds()
<dtml-else> not in objectIds()
</dtml-if>

#in PageTemplates, NOTE: you are returning the *actual* instance
<span tal:replace="python:test(hasattr(here, myId), getattr(here, myId), 'object not found')" />

# EXPLICIT: 
# getattr/hasattr checks acquistion, if you want to explictly
# check a folder if it has a object you .aq_explicit

# Script(Python)
f = context.myFolder
if getattr(f.aq_explicit, myId, 0): return myId + ' exists!'

#DTML
<dtml-if "_.hasattr(this().aq_explicit, myId)"> <dtml-var myId> exists
<dtml-else> doesnt exist
</dtml-if>

#if you want to check the parent folder you can, go up the acqusition
#chain using aq_parent

f = context.myFolder
if getattr(f.aq_parent.aq_explicit, myId, 0): return 'exists'
return 'nope'

#this will check explicitly myFolder's parent directory for myId


#we can also use ZDOM
f = context.myFolder
if getattr(f.getParentNode().aq_explicit, myId, 0): return 'exists'
return 'nope'

#if you want to programatically acquire lets say, a Property from the Acquistion
#chain you can use 
propertyValue=object.aq_acquire('propertyId')