Question: How can I format a hex string ('003de70fc98a') to a MAC string ('00:3d:e7:0f:c9:8a') using a concise statement?

Answer: 
You could use a regex:

```
>>> re.sub(r'(?<=..)(..)', r':\1', '003de70fc98a')
'00:3d:e7:0f:c9:8a'

```
Try this:

```
s = '003de70fc98a'
':'.join(s[i]+s[i+1] for i in range(0, len(s), 2))
=> '00:3d:e7:0f:c9:8a'

```