Python greedy matching and multi-line matching

The following is an example explanation of greedy matching and multi-line matching in python. It has a good reference value and I hope it will be helpful to everyone. Let’s take a look together

1 Non-greedy flag

>>> re.findall(r"a(\d+?)", "a23b")
  ['2']
>>> re.findall(r"a(\d+)", "a23b")
  ['23']

Pay attention to compare this Situation:

>>> re.findall(r"a(\d+)b", "a23b")
  ['23']
>>> re.findall(r"a(\d+?)b", "a23b")
  ['23']

2 If you want to match multiple lines, add the re.S and re.M flags

re.S:. Will match newline characters. Default. Will not match newline characters.

>>> re.findall(r"a(\d+)b.+a(\d+)b", "a23b\na34b")
  []
>>> re.findall(r"a(\d+)b.+a(\d+)b", "a23b\na34b", re.S)
  [('23', '34')]
>>>

re.M: ^ The $ flag will match every line. By default ^ and $ will only match the first line

>>> re.findall(r"^a(\d+)b", "a23b\na34b")
  ['23']
>>> re.findall(r"^a(\d+)b", "a23b\na34b", re.M)
  ['23', '34']

However, if there is no ^ flag,

>>> re.findall(r"a(\d+)b", "a23b\na23b")
  ['23', '23']

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