Question

help with optional reading think python exercise 8.2. How do I slice and insert new dna into a string and splice it back together again?
code attached:
#http://www.greenteapress.com/thinkpython/thinkpython.pdf
#chapter 8 for loops
#brandon MOOC group 3
#oct. 20

prefixes = 'JKLMNOPQ'
suffix = 'ack'
news=[]
for letter in prefixes:
news.append( letter + suffix)
print news
for each word in news
if [:1] == 'O': #finds Oack in the list
#code to mutate Oack to Ouack
elif [:1] == "Q": #finds Qack in the list
#code to insert u before ack

Answer 1

Like this ?

prefixes = 'JKLMNOPQ'
suffix = 'ack'
news=[]
for letter in prefixes:
if letter == 'O' or letter == 'Q':
letter += 'u'
news.append( letter + suffix)
print news

Answer 2

Btw, if you really want to "insert" a char into a String, as strings are immutable, you should probably do like this : word = word[0] + 'u' + word[1:], but then you have to replace the word in the list :

for index, word in enumerate(news):
if word[0] in ['O', 'Q']:
word = word[0] + 'u' + word[1:]
news[index] = word
print news

Answer 3

Since you've already put it into a list, I would opt to use the list splice method...

for i in range(0, len(news)):
letter=news[i][:1]
if letter=='O'or letter=='Q':
news[i]=news[i][:1]+'u'+news[i][1:]

As @FabienToune put it, you will need to replace the word after changing it.