在python中使用正则表达式提取实体

Question

What I have: "peak hour traffic at location1 towards location2 , location3 towards location4 and location5 towards location6 ."

example: "peak hour traffic at ulsoor lake jn towards nagatheatre jn, okalipuram towards majestic and bamboo bazaar jn towards cole's park jn."

What I want: extract locations using regex in python.

example:

[('ulsoor lake jn', 'nagatheatre jn'), ('okalipuram', 'majestic'), ('bamboo bazaar jn', "cole's park jn")]

what I have done:

>>> regex1 = '(?:\sat\s|,|and)(.*) towards (.*)(?:\.|,|and)'
>>> re.search(regex1, "peak hour traffic at ulsoor lake jn towards nagatheatre jn, okalipuram towards majestic and bamboo bazaar jn towards cole's park jn.").groups()
15: ('ulsoor lake jn towards nagatheatre jn, okalipuram towards majestic and bamboo bazaar jn',
"cole's park jn")

What I am getting :

('ulsoor lake jn towards nagatheatre jn, okalipuram towards majestic and bamboo bazaar jn', "cole's park jn")

As it can be seen it's only matching the external expression when there are sub-expression that matches the pattern. Please help. Thank You.

Answer 1

You actually need a couple of things. First - like my comment said - use (.*?) instead of (.*) so that your captures are not greedy.

Second - use a look-ahead assertion so you don't advance the parser when determing where a capture ends,

Third - use findall instead of search .

>>> r = re.compile('(?:\sat\s|,|and)(.*?) towards (.*?)(?=\.|,|and)')
>>> s = "peak hour traffic at ulsoor lake jn towards nagatheatre jn, okalipuram towards majestic and bamboo bazaar jn to wards cole's park jn."
>>>
>>> r.findall(s)
[('ulsoor lake jn', 'nagatheatre jn'), (' okalipuram', 'majestic '), (' bamboo bazaar jn', "cole's park jn")]