Precedence

Write a function, named determine$\_$precedence, that takes a schedule $($a list of Actions $($see previous problem$)).$

This function should return a list of precendences between transactions as determined by conflicts.

Each precedence is a tuple $($pair$)$ with the first element being the transaction that must precede the second

$($element$)$ transaction. Please sort the precedences before returning them $($transactions will be strings$).$

Note: You are welcome to use the solution from previous questions.

Hint: You may find it useful to use itertools library in this question:

tests:

import sqlite$3$

import unittest

from pprint import pprint

import sys

import os

sys$.$path.append$("/$home$/$codio$/$workspace$/$student$\_$code$/")$

from precedence import determine$\_$precedence

class Action:

def $\_\_$init$\_\_($self$,$ object$\_,$ transaction, is$\_$write$)$:

self.object$\_=$ object$\_$

self.transaction $=$ transaction

self.is$\_$write $=$ is$\_$write

def $\_\_$str$\_\_($self$)$:

return f$"$Action$(\{$self$.$object$\_\},\{$self$.$transaction$\},\{$self$.$is$\_$write$\})"$

$\_\_$repr$\_\_=\_\_$str$\_\_$

class TestPrecedence$($unittest$.$TestCase$)$:

def test$\_$visible$\_1($self$)$:

actions $=[$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$False$),$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$True$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

$]$

print$("$Actions:$")$

pprint$($actions$)$

result $=$ determine$\_$precedence$($actions$)$

print$("$Result:$")$

pprint$($result$)$

print$("$Expected:$")$

expected $=[(\text{'}$T$1\text{'},\text{'}$T$2\text{'}),(\text{'}$T$2\text{'},\text{'}$T$3\text{'})]$

pprint$($expected$)$

assert expected $==$ result

def test$\_$visible$\_2($self$)$:

actions $=[$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$False$),$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$False$),$

Action$($object$\_="$C$",$ transaction$="$T$3",$ is$\_$write$=$True$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$True$),$

Action$($object$\_="$C$",$ transaction$="$T$1",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

$]$

print$("$Actions:$")$

pprint$($actions$)$

result $=$ determine$\_$precedence$($actions$)$

print$("$Result:$")$

pprint$($result$)$

print$("$Expected:$")$

expected $=[(\text{'}$T$1\text{'},\text{'}$T$2\text{'}),(\text{'}$T$2\text{'},\text{'}$T$3\text{'}),(\text{'}$T$3\text{'},\text{'}$T$1\text{'})]$

pprint$($expected$)$

assert expected $==$ result

def test$\_$visible$\_3($self$)$:

actions $=[$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$False$),$

Action$($object$\_="$A$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$False$),$

Action$($object$\_="$C$",$ transaction$="$T$3",$ is$\_$write$=$True$),$

Action$($object$\_="$B$",$ transaction$="$T$1",$ is$\_$write$=$True$),$

Action$($object$\_="$B$",$ transaction$="$T$4",$ is$\_$write$=$True$),$

Action$($object$\_="$A$",$ transaction$="$T$3",$ is$\_$write$=$True$),$

Action$($object$\_="$C$",$ transaction$="$T$1",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$4",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$False$),$

Action$($object$\_="$B$",$ transaction$="$T$2",$ is$\_$write$=$True$),$

$]$

print$("$Actions:$")$

pprint$($actions$)$

result $=$ determine$\_$precedence$($actions$)$

print$("$Result:$")$

pprint$($result$)$

print$("$Expected:$")$

expected $=[(\text{'}$T$1\text{'},\text{'}$T$2\text{'}),(\text{'}$T$1\text{'},\text{'}$T$4\text{'}),(\text{'}$T$2\text{'},\text{'}$T$3\text{'}),(\text{'}$T$3\text{'},\text{'}$T$1\text{'}),(\text{'}$T$4\text{'},\text{'}$T$2\text{'})]$

pprint$($expected$)$

assert expected $==$ result

if $\_\_$name$\_\_==\text{'}\_\_$main$\_\_\text{'}$:

unittest.main$()$