Recursion question

Question

pythonlearning 0 Light Poster

13 Years Ago

just write this function for a recursion trace back, but it become a infinite loop and won't get into the next level of recursion. I cannot find the problem, many thanks! p_value gotten from a matrix outside, tested that and it is OK. status, i, j pass form main and start is (1,5,4).

def traceback_alignment(status, i, j):
alignmentA=""
alignmentB=""
p_value=0
while (i>1 and j>1):
if status==1:
alignmentA=seqA[i-1]+alignmentA
alignmentB=seqB[j-1]+alignmentB
p_value=ptr_matrixM.__getitem__(j, i)
print ("p_value="+str(p_value))
if status==2:
alignmentA=seqA[i-1]+alignmentA
alignmentB="_"+alignmentB
p_value=ptr_matrixIx.__getitem__(j, i)
print ("p_value="+str(p_value))
if status==3:
alignmentA="_"+alignmentA
alignmentB=seqB[j-1]+alignmentB
p_value=ptr_matrixIy.__getitem__(j, i)
print ("p_value="+str(p_value))

if p_value==1:
traceback_alignment(2, i-1, j)
if p_value==2:
traceback_alignment(3, i, j-1)
if p_value==4:
traceback_alignment(1, i-1, j-1)
if p_value==5:
traceback_alignment(2, i-1, j)
traceback_alignment(1, i-1, j-1)
if p_value==6:
traceback_alignment(1, i-1, j-1)
traceback_alignment(3, i, j-1)
if p_value==7:
traceback_alignment(3, i, j-1)
traceback_alignment(2, i-1, j)
traceback_alignment(1, i-1, j-1)
return (alignmentA, alignmentB)

python

2 Contributors
6 Replies
75 Views
9 Hours Discussion Span
Latest Post 13 Years Ago Latest Post by Gribouillis

All 6 Replies

Gribouillis 1,391 Programming Explorer

13 Years Ago

Pleas, learn about code tags here http://www.daniweb.com/forums/announcement.php?f=8&announcementid=3 and repost your code accordingly.

Gribouillis 1,391 Programming Explorer

13 Years Ago

The first problem I see is that the values of i and j are never modified, so I don't know how you can leave the loop while (i>4 and j>4) . Also if you could add some more code so that it would be runnable, that would help.

Reply to this topic

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.

pythonlearning 0 Light Poster · Answer 1 · 2010-10-06T16:33:32+00:00

Sorry, hope it will work

def traceback_alignment(status, i, j):
alignmentA=""
alignmentB=""
p_value=0
while (i>4 and j>4):
if status==1:
alignmentA=seqA[i-1]+alignmentA
alignmentB=seqB[j-1]+alignmentB
print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
p_value=ptr_matrixM.__getitem__(j, i)
print ("p_value="+str(p_value))
if status==2:
alignmentA=seqA[i-1]+alignmentA
alignmentB="_"+alignmentB
print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
p_value=ptr_matrixIx.__getitem__(j, i)
print ("p_value="+str(p_value))
if status==3:
alignmentA="_"+alignmentA
alignmentB=seqB[j-1]+alignmentB
print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
p_value=ptr_matrixIy.__getitem__(j, i)
print ("p_value="+str(p_value))

if p_value==1:
traceback_alignment(2, i-1, j)
if p_value==2:
traceback_alignment(3, i, j-1)
if p_value==4:
traceback_alignment(1, i-1, j-1)
if p_value==5:
traceback_alignment(2, i-1, j)
traceback_alignment(1, i-1, j-1)
if p_value==6:
traceback_alignment(1, i-1, j-1)
traceback_alignment(3, i, j-1)
if p_value==7:
traceback_alignment(3, i, j-1)
traceback_alignment(2, i-1, j)
traceback_alignment(1, i-1, j-1)
return (alignmentA, alignmentB)

pythonlearning 0 Light Poster · Answer 2 · 2010-10-06T16:38:06+00:00

def traceback_alignment(status, i, j):
    alignmentA=""
    alignmentB=""
    p_value=0
    while (i>4 and j>4):
        if status==1:
            alignmentA=seqA[i-1]+alignmentA
            alignmentB=seqB[j-1]+alignmentB
            print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
            p_value=ptr_matrixM.__getitem__(j, i)
            print ("p_value="+str(p_value))
        if status==2:
            alignmentA=seqA[i-1]+alignmentA
            alignmentB="_"+alignmentB
            print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
            p_value=ptr_matrixIx.__getitem__(j, i)
            print ("p_value="+str(p_value))
        if status==3:
            alignmentA="_"+alignmentA
            alignmentB=seqB[j-1]+alignmentB
            print ("in While i="+str(i), "j="+str(j), "alignmentA="+alignmentA, "alignmentB="+alignmentB, "Status="+str(status))
            p_value=ptr_matrixIy.__getitem__(j, i)
            print ("p_value="+str(p_value))

        if p_value==1:
            traceback_alignment(2, i-1, j)
        if p_value==2:
            traceback_alignment(3, i, j-1)
        if p_value==4:
            traceback_alignment(1, i-1, j-1)
        if p_value==5:
            traceback_alignment(2, i-1, j)
            traceback_alignment(1, i-1, j-1)
        if p_value==6:
            traceback_alignment(1, i-1, j-1)
            traceback_alignment(3, i, j-1)
        if p_value==7:
            traceback_alignment(3, i, j-1)
            traceback_alignment(2, i-1, j)
            traceback_alignment(1, i-1, j-1)
    return (alignmentA, alignmentB)

pythonlearning 0 Light Poster · Answer 3 · 2010-10-06T18:20:18+00:00

When it gets into recursion, j and i should change, right? p_value is always one of numbers 1-7. Thanks and I will try to get more code on.

Gribouillis 1,391 Programming Explorer Team Colleague · Answer 4 · 2010-10-06T19:14:42+00:00

When it gets into recursion, j and i should change, right? p_value is always one of numbers 1-7. Thanks and I will try to get more code on.

i and j cannot change upon recursion because python functions are always called by value.

Recursion question

Recommended Answers Collapse Answers

All 6 Replies

Recommended Answers