python regular expression sub only one position code example
Example 1: python replace regex
import re
s = "Example String"
replaced = re.sub('[ES]', 'a', s)
print replaced
# will print 'axample atring'
Example 2: python re compile
import re
# Compile a regular expression pattern into a regular expression object, which can be used for matching using its match(), search() and other methods, described below.
prog = re.compile(pattern)
result = prog.match(string)
# is equivalent to
result = re.match(pattern, string)