how to insert a string into a string of random letters in a for loop

[aboxylica]

I have a code in which i create a set of alphabets of specified count .Now in particular positions in it i want to embed my choice of letters how do i do it.here is my code

def random_seq():
    seq=""
    ch=""
    for i in range(0,50):
        ch=random.choice(("ATGC"))
        seq=seq+ch
        for i in seq:
            
            seq[i:i+15]="CGTCAAGTTCAAGTGC"
    return seq

now here in this I am creating a list of sequence containing the letters only "ATGC".Now I want to specify in this that say at particular postions like say the first fifteen characters should be what i mentioned. and say i also want to do when for positions from 41 to 50 i want a specifies set of letters something like this " "CGTCAAGTTCAAGT GC".how to do this?
why is my code not working?
waiting for your reply
cheers!

[bartonc]

I have a code in which i create a set of alphabets of specified count .Now in particular positions in it i want to embed my choice of letters how do i do it.here is my code

def random_seq():
    seq=""
    ch=""
    for i in range(0,50):
        ch=random.choice(("ATGC"))
        seq=seq+ch
        for i in seq:
            
            seq[i:i+15]="CGTCAAGTTCAAGTGC"
    return seq

now here in this I am creating a list of sequence containing the letters only "ATGC".Now I want to specify in this that say at particular postions like say the first fifteen characters should be what i mentioned. and say i also want to do when for positions from 41 to 50 i want a specifies set of letters something like this " "CGTCAAGTTCAAGT GC".how to do this?
why is my code not working?
waiting for your reply
cheers!

I hope this is what you are looking for:[CODE=python]import random

def random_seq(nCha rs, insertAt, aString):
seq = ""
for i in range(nChars):
if i == insertAt:
seq += aString
ch=random.choic e(("ATGC"))
seq += ch
return seq

# I put markers in your string so you can see and make it an argurment to the function
theStringToInse rt = "#CGTCAAGTTCAAG TGC#"
# calculate the count as total - the length of the string to insert
count = 50 - len(theStringTo Insert)


result = random_seq(coun t, 15, theStringToInse rt)
print result, "is %d characters long" %len(result)
print result.find('#' )
[/CODE]TATGTAGATACAGCT #CGTCAAGTTCAAGT GC#CGGGGTAGCCCG TTCAT is 50 characters long
15

[aboxylica]

Thanks a lot!that helped.But I still have that matrix problem.
waiting for ur reply,
cheers!

I hope this is what you are looking for:[CODE=python]import random

def random_seq(nCha rs, insertAt, aString):
seq = ""
for i in range(nChars):
if i == insertAt:
seq += aString
ch=random.choic e(("ATGC"))
seq += ch
return seq

# I put markers in your string so you can see and make it an argurment to the function
theStringToInse rt = "#CGTCAAGTTCAAG TGC#"
# calculate the count as total - the length of the string to insert
count = 50 - len(theStringTo Insert)


result = random_seq(coun t, 15, theStringToInse rt)
print result, "is %d characters long" %len(result)
print result.find('#' )
[/CODE]TATGTAGATACAGCT #CGTCAAGTTCAAGT GC#CGGGGTAGCCCG TTCAT is 50 characters long
15