not sure about python but this will read a text file and open windows let me see if I can get tabs for you though
set locations to paragraphs of (read (choose file with prompt "Pick text file containing urls"))
repeat with aline in locations
if length of aline is greater than 0 then
tell application "Safari"
make new document at end of documents
set URL of document 1 to aline
end tell
end if
end repeat
EDIT:
Ok this is better and it opens them in tabs of a single window
set locations to paragraphs of (read (choose file with prompt "Pick text file containing urls"))
tell application "Safari"
activate
set adoc to make new document
end tell
repeat with aline in locations
if length of aline is greater than 0 then
tell application "Safari" to make new tab at end of window 1 with properties {URL:aline}
end if
end repeat
New Addtion
this is yet another way based on regulus6633's post in conjunction with mine
set locations to paragraphs of (read (choose file with prompt "Pick text file containing urls"))
repeat with aLocation in locations
tell application "Safari" to open location aLocation
end repeat