Replace match after the start of the line and another pattern

Question

I'm trying to delete a character that is at the start of the line of multiple string, but, also have another pattern just before the start of the line, which i don't want to delete:

1:string:test...
2:string test
3:etc...

to

1 string:test...
2 string test
3 etc...

Some string can also contain the character : which make things interesting. So far i tried:

echo "1:test:" | grep -Pv '(?<=\d):'

which does match the : character (at least it highlight it, so I'm guessing it's matched) but it doesn't get omitted when using the -v flag, maybe because it's on the same line as the match? (Here i only did experiment on how to match it and remove it instead of replacing it with a space, as the aforementioned example showed)

echo "1:test:" | sed 's/^.:./ /g'

This seems to be the closest i got, but it cut off the rest of the start beside the : character, which give:

est:

instead of

1 test:

Answer 1

this works:

echo -e "1:test:\n2:test\n3:test:\n" | sed '/:/s// /'

Print

1 test:
2 test
3 test:

Answer 2

Python

#!/usr/bin/python
import re
k=re.compile(":")
m=open('filename','r')
for i in m:
    print i.replace(":"," ",1).strip()

awk command works only for mentioned example

awk  -F ":" '{print substr($0,1,1),substr($0,3)}' filename

sed command

  sed "s/:/ /1" filename