Increment variable within for loop

Question

I am new to Python and am trying to figure out how to address the following issue. I have two lists, list1 looks like this:

['10','12','12','23]

And list2 looks like this:

['15','16','13','15']

I also have a dictionary consisting of the following key-values:

dictionary = {
'10': 'AATGCGTAAGCTAGCGATAGATGCAACGTT', 
'12': 'GGTCAGAGTTTATCGGTATGTTAGCATGGA', 
'23': 'ATGGGCGCGTATATTAAAGGCGCCGCCCTG'
}

The keys in this dictionary consist of those elements in list1. Each element in list1 is also associated with a single element in list2 (in order, such that '10' in list1 is associated with '15' in list2, '12' in list1 with '16' in list2, etc.).

For each element in list1, I would like to take the associated dictionary value, and insert characters into specific positions using the associated element in list2 to determine the positions. So far I've been working on a for loop to do this:

for i in list1:
    dict_key = dictionary.get(i)
    pos = int(list2[0])
    full = dict_key[:pos] + '[' + dict_key[pos] + ']' +  dict_key[(pos+1):]
    print(full)

I would like my final output to look like this:

AATGCGTAAGCTAGC[G]ATAGATGCAACGTT
GGTCAGAGTTTATCGG[T]ATGTTAGCATGGA
GGTCAGAGTTTAT[C]GGTATGTTAGCATGGA
ATGGGCGCGTATATT[A]AAGGCGCCGCCCTG

But my output currently looks like this because I am specifically calling for only index 0 from list2:

AATGCGTAAGCTAGC[G]ATAGATGCAACGTT
GGTCAGAGTTTATCG[G]TATGTTAGCATGGA
GGTCAGAGTTTATCG[G]TATGTTAGCATGGA
ATGGGCGCGTATATT[A]AAGGCGCCGCCCTG

I want to increase the element that's called for in list2 by 1 with each iteration of the loop, but I can't seem to figure it out. Should I define a new variable using range? Any comments will be appreciated!

Randy · Accepted Answer · 2016-11-08 20:46:25Z

2

Just change for i in list1: to for i, pos in zip(list1, list2): and remove the assignment of pos in the second line of the loop. zip will let you iterate through both lists at once.

answered Nov 8, 2016 at 20:46

Randy

14.9k3 gold badges40 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

nrcombs Over a year ago

Thanks for this solution @Randy C! Very simple and does what I wanted, will also be helpful to know in general. Thanks again!

enigma · Accepted Answer · 2016-11-08 20:52:13Z

1

Using enumerate is helpful in situations like this - it gives you a tuple containing the position of each element, and the element itself. Note, I've changed your meaning of i to mean the element's position rather than the element.

Your variable dict_key would probably be better called dict_value, since the element in list1 is actually the key that you are looking up in dictionary.

for i, el in enumerate(list1):
    dict_value = dictionary.get(el)
    pos = int(list2[i])
    full = dict_value[:pos] + '[' + dict_value[pos] + ']' +  dict_value[(pos+1):]
    print(full)

edited Nov 8, 2016 at 20:52

answered Nov 8, 2016 at 20:46

enigma

3,5012 gold badges19 silver badges31 bronze badges

1 Comment

nrcombs Over a year ago

Also very helpful, thanks @enigma, I had not previously used enumerate.

tdelaney · Accepted Answer · 2016-11-08 20:58:35Z

0

You can build iterators for your lists (int(i) for i in list2 for instance iterates list2, converting its values to int on the way) and use zip to read them in pairs.

list1 = ['10','12','12','23']
list2 = ['15','16','13','15']

dictionary = {
'10': 'AATGCGTAAGCTAGCGATAGATGCAACGTT', 
'12': 'GGTCAGAGTTTATCGGTATGTTAGCATGGA', 
'23': 'ATGGGCGCGTATATTAAAGGCGCCGCCCTG'
}

for val, pos in zip((dictionary[j] for j in list1), (int(i) for i in list2)):
    full = val[:pos] + '[' + val[pos] + ']' +  val[(pos+1):]
    print(full)

Some people would prefer string formatting to build the resulting string

full = '{}[{}]{}'.format(val[:pos], val[pos], val[pos+1:])

but that's personal taste.

answered Nov 8, 2016 at 20:58

tdelaney

77.9k6 gold badges91 silver badges129 bronze badges

1 Comment

nrcombs Over a year ago

Thanks @tdelaney, gives me what I want and I now know about list iterators.

Collectives™ on Stack Overflow

Increment variable within for loop

3 Answers 3

1 Comment

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related