如何打印另一个字符串中某些字符第一次出现的索引？

Question

I'm trying to make a function made up of two strings:

def find_firstchars( chars, wholestring )

Which, when printed, returns the positions of each of those characters in the char string. The first character in "chars" must mark the beginning of the index for the next character, so A is indexed first, then the function carries on indexing the next character after that position, and so on.

There may be multiple occurrences of the "chars" string in "wholestring", but I only need to index the characters of the first one.

For example,

print (find_firstchars( "ABC", "VMQOAJVBKRJCPGI" )

Would return the position list: [4, 7, 11]

I've tried something like the code below, and beside the error I get in console for this about slice indices needing to be integers, I'm not sure how to efficiently search for each character in the following string.

def find_firstchars(chars, wholestring):
    index = 0 # Initializing index
    splice = [] # Initializing list
    while index != -1: # Run until at end of index
        index = chars.find(chars,wholestring) # Finds index value of each char in subsequence
        if index != -1: # If not at end:
            splice.append(index) # Append index value to splice list,
            index += 1 # Then keep looking
    return splice
print (find_firstchars("GTA", "ACGACATCACGTGACG"))

Though this should print [2, 6, 8].

Answer 1

You are close:

def find_firstchars(chars, wholestring):
    index = 0 # Initializing index
    splice = [] # Initializing list
    for c in chars:
        index = wholestring.find(c,index)
        splice.append(index)
        index += 1 # Then keep looking
    return splice
print (find_firstchars("GTA", "ACGACATCACGTGACG"))