兩個問題
b. 如何提取這些頁面的發帖時間
分析：
發現很有規律。規則差不多是這樣：
發帖時間都這樣的：[2008-08-09 14:51:35]
規則：\[ (\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d)\]
regular expression syntax
syntax
explanation
characters c
the character c
\ unnnn , \ xnn,
\ 0n , \ 0nn , \ 0nnn
the code unit with the given hex or octal value
\ t, \ n, \ r, \ f, \ a, \e
the control characters tab, newline, return, form feed, alert, and escape
\ cc
the control character corresponding to the character c
character classes [
c1c2 . . .]
any of the characters represented by c
1 , c
2 , . . . the ci
are characters, character ranges (c
1 -c
2 ), or character classes
[^ . . .]
complement of character class
[ . . . && . . .]
intersection of two character classes
predefined character classes .
any character except line terminators (or any character if the dotall flag is set)\d
a digit [0-9 ]\d
a nondigit [^0-9 ]\s
a whitespace character [ \t\n\r\f\x0b ]\s
a non-whitespace character\w
a word character [a-za-z0-9 _]\w
a nonword character\p
a named character class—see table 12-9 \p
the complement of a named character class
boundary matchers
^ $beginning, end of input (or beginning, end of line in multiline mode)\b
a word boundary\b
a nonword boundary
syntax
explanation \a
beginning of input\z
end of input\z
end of input except final line terminator\g
end of previous match
quantifiers x?
optional x
x*x, 0 or more times
x +x, 1 or more times
x x x
x n times, at least n times, between n and m times
quantifier suffixes ?
turn default (greedy) match into reluctant match+
turn default (greedy) match into possessive match
set operations xy
any string from x , followed by any string from y
x|yany string from x or y
grouping
(x)capture the string matching x as a group\n
the match of the n th group
escapes \
c the character c (must not be an alphabetic character)\q
. . . \e
quote . . . verbatim
(? . . . )
special construct—see api notes of pattern class
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