正则表达式-用大写字母替换所有匹配项

Question

How do I uppercase every matching occurrence? Each two letter combo, first upper, second lower, where they are surrounded by a space or begin/end of string.

re.sub('( |^)[A-Z][a-z]($| )', lambda m: m.group(0).upper(), loc) 

works with

loc = ' Ny' # or ' Ny ' or 'Ny '

but not

loc = ' Ny Us'

I'd like the results to be NY and NY US

I'm working in Python 2.7.

Answer 1

You may convert the last group to a lookahead:

re.sub('( |^)[A-Z][a-z](?=$| )', lambda m: m.group(0).upper(), loc)
                       ^^^^^^^

See the Python demo .

The point is to allow the regex engine to match the space after the last letter that was matched at the previous iteration.

Here is an alternative regex based on lookarounds that you may use for the same task:

r'(?<!\S)[A-Z][a-z](?!\S)'

See this regex demo . The (?<!\\S) negative lookbehind requires the position at the start of a string or the one that is preceded with a whitespace. The (?!\\S) negative lookahead requires the end of string position or a whitespace immediately to the right of the current location.