Convert a list "of positions" into a string

[DRKT]

Hello everybody,

I managed to convert a string of a given lenght consisting of 2 numbers only (0 and 1) into a list of positions of the number '1', (see example below).
Note: The string size is always going to be a multiple of 4!

Example for string lenght equals 8:
>>> string = "01010100"
>>> [i for i in range(len(strin g)) if string.startswi th('1', i)]
[1, 3, 5]

Problem:
I would like to "back calculate" the original string "01010100" from the list of positions [1, 3, 5]

Means: convert the list [1, 3, 5] back to a string 01010100

Your help is appreciated.

[DRKT]

P.S. I am using python 3.5

[dwblas]

it's just a simple replace

b_string=["0" for ctr in range(8)]
positions=[1, 3, 5]
for position in positions:
    b_string[position]="1"
print b_string

[DRKT]

The above "simple replacement does almost the right thing but
1st: it gives n results for n positions
result of above code is:
['0', '1', '0', '0', '0', '0', '0', '0']
['0', '1', '0', '1', '0', '0', '0', '0']
['0', '1', '0', '1', '0', '1', '0', '0']
and 2nd:
it prints out a list not a string!

I would need to have a single result string like this:
"01010100"

[dwblas]

For #2, use "".join(the_lis t") to convert http://www.tutorialspoint.com/python/string_join.htm For #1, lists use offsets, so the first element is at zero offset (at the beginning). The second element is at offset one (skip over the first/go to the end of the first=start of second in memory), etc. So 3 would skip to the beginning of the 4th element. Adjust the numbers accordingly (num-1? don't understand exactly what you are saying). This can also be done with strings by using a for loop and adding each character to a new string unless it is at one of the replacements, and then add the "1 instead, but using a list is much more straight forward.