Code:

from pyfbsdk import *

# initialize the needed variables

lScene = FBSystem().Scene

for lcon in lScene.Components:
    if lcon:
        # searching for constraint with Toe in name
        if lcon.Name.find("Toe") != -1:
            if lcon.ClassName() == "FBConstraint":
             # got it, so print name to check
             print (lcon.Name + " " +lcon.ClassName()+"\n\n")
             #ok now find its active properties to set
             fCon = lcon.PropertyList.Find("Active")
             #print it so we know what it was for debug
             print fCon.Data
             #set it to 0 to deactiave it
             fCon.Data = 0
             #print it agian to see if it changed for debuging
             print fCon.Data
             # deactivate the constraint.

Code:

from pyfbsdk import FBConstraintManager

# Initialize the constraint manager
lConstraintManager = FBConstraintManager()
# get the number of constraints
count = lConstraintManager.ConstraintGetCount()
lTargetName = 'test' # just a sample name - this could be passed as an arg.

counter = 0
while counter < count:  # iterate through the list of constraints
    iConstraint = lConstraintManager.ConstraintGet( counter )
    if iConstraint.Name == lTargetName:
        print 'Turning %s(%s) OFF'%(iConstraint.Name, iConstraint.Description)
        iConstraint.SetActive( False )
    counter += 1

del( FBConstraintManager )