Python中Lua string.gsub的最佳替代功能是什么？

Question

What's the best alternative function of Lua 's global pattern substitution function string.gsub(s, pattern, function) in Python ? eg

> string.gsub("banana", "(a)(n)", function(a,b) return b..a end) -- reverse any "an"s
bnanaa  2

UPDATE : I'd like to implement a complex function during pattern substitution in Python like Lua's string.gsub , which can be implemented by Python's re.sub with function or lambda expr .

Answer 1

As string.gsub(s, pattern, replace [, n]) returns a pair of values, the modified string and the number of substitutions made , in Python, you need to use re.subn :

re.subn(pattern, repl, string, count=0, flags=0)
Perform the same operation as sub() , but return a tuple ( new_string, number_of_subs_made ).

See a Python demo :

import re
print (re.subn("(a)(n)", r"\2\1", "banana"))
# => ('bnanaa', 2)

And you also may use an anonymous method (or a lambda expression for simpler scenarios) as a replacement argument:

print (re.subn("(a)(n)", lambda m: "{}{}".format(m.group(2), m.group(1)), "banana"))
# => ('bnanaa', 2)

See another Python demo .

NOTE : If you need no number of replacements made, use a mere re.sub .