Using regex to findall lowercase letters in string append to list. Python

Question

I'm looking for a way to get the lowercase values out of a string that has both uppercase and potentially lowercase letters here's an example ``` sequences = ['CABCABCABdefgdefgdefgCABCAB','FEGFEGFEGwowhelloFEGFEGonemoreFEG','NONEARELOWERCASE'] #sequences with uppercase and potentially lowercase letters ``` this is what i want to output ``` upper_output = ['CABCABCABCABCAB','FEGFEGFEGFEGFEGFEG','NONEARELOWERCASE'] #the upper case letters joined together lower_output = [['defgdefgdefg'],['wowhello','onemore'],[]] #the lower case letters in lists within lists lower_indx = [[9],[9,23],[]] #where the lower case values occur in the original sequence ``` so i want the lower_output list be a LIST of SUBLISTS. the SUBLISTS would have all the strings of lowercase letters . i was thinking of using regex . . . ``` import re lower_indx = [] for seq in sequences: lower_indx.append(re.findall("[a-z]", seq).start()) print lower_indx ``` for the lowercase lists i was trying: ``` lower_output = [] for…

Accepted Answer

Sounds like (I may be misunderstanding your question) you just need to capture runs of lowercase letters, rather than each individual lowercase letter. This is easy: just add the `+` quantifier to your regular expression.

```
for seq in sequences:
    lower_output.append(re.findall("[a-z]+", seq)) # add substrings
```

The `+` quantifier specifies that you want "at least one, and as many as you can find in a row" of the preceding expression (in this case `'[a-z]'`). So this will capture your full runs of lowercase letters all in one group, which should cause them to appear as you want them to in your output lists.

It gets a little big uglier if you want to preserve your list-of-list structure and get the indices as well, but it's still very simple:

```
for seq in sequences:
    matches = re.finditer("[a-z]+", seq) # List of Match objects.
    lower_output.append([match.group(0) for match in matches]) # add substrings
    lower_indx.append([match.start(0) for match in matches]) # add indices

print lower_output
>>> [['defgdefgdefg'], ['wowhello', 'onemore'], []]

print lower_indx
>>> [[9], [9, 23], []]
```

Using regex to findall lowercase letters in string append to list. Python

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