建立日期: 2021/12/13
修改日期: 2021/12/17
WIN10 / Python 3.9.9
前言
前面談到 Python 的正則式定義, 現在就讓我們來看一些正則式的例項, 本文會按例項的增加而持續更新; 另外為了說明正則式的內容, 所以大都採用了 re.VERBOSE 方式來書寫正則式.
例項一 網頁內容擷取, 小說目錄各章節的標題及鏈結網址
- 讀取小說目錄的網頁內容
from urllib.request import urlopen
url = 'https://www.ptwxz.com/html/11/11175/'
html = urlopen(url).read().decode('gbk')>>> html
('<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
...
'<h1>萬界最強道長最新章節</h1>\r\n'
'</div>\r\n'
...
'<li><a href="8011051.html">第1章 倚天峰上</a></li>\r\n'
'<li><a href="8011052.html">第2章 萬界道士</a></li>\r\n'
...
'<li><a href="8050881.html">第55章 隻身誘敵</a></li>\r\n'
'<li><a href="8052105.html">第56章 終章</a></li>\r\n'
...
'</body>\r\n'
'</html>\r\n')一般我們會使用 bs4.BeautifulSoup 來處理, 看似比較簡單, 但實際上, 並不一定如此, 這裡使用正則式, 其結果更簡單.
- 擷取書名
import re
# <h1>萬界最強道長最新章節</h1>
title_regex = re.compile(r"""
<h1> # <h1>
(.*?) # 萬界最強道長, group(1)
.{4} # 最新章節
</h1> # </h1>
""", re.VERBOSE)
title = title_regex.search(html).group(1)
print(f'小說書名: {title}')小說書名: 萬界最強道長- 擷取各章節的鏈結及章名
# <li><a href="8011051.html">第1章 倚天峰上</a></li>
chapter_regex = re.compile(r"""
<li><a # <li><a
\s+ # ' '
href=" # href="
(.+?)" # 8011051.html, group(1) 鏈結
> # >
(.+?) # 第1章 倚天峰上, group(2) 章名
</a></li> # </a></li>
""", re.VERBOSE)
chapters = [(url+m.group(1), m.group(2)) for m in chapter_regex.finditer(html)]
for chapter in chapters:
print(chapter)('https://www.ptwxz.com/html/11/11175/8011051.html', '第1章 倚天峰上')
('https://www.ptwxz.com/html/11/11175/8011052.html', '第2章 萬界道士')
...
('https://www.ptwxz.com/html/11/11175/8050881.html', '第55章 隻身誘敵')
('https://www.ptwxz.com/html/11/11175/8052105.html', '第56章 終章')- 擷取第一章的內容
import re
from urllib.request import urlopen
url = 'https://www.ptwxz.com/html/11/11175/8011051.html'
html = urlopen(url).read().decode('gbk')<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
...
青天白日，浩浩諸峰。<br /><br /> 悠悠鐘聲，迴盪山間。
...
<br /><br /> 陳玄一身子一傾，倒在了地上。
</div>
...
</html>就以\ \ \ \ 為起點, </div>為終點, 取出章節內容, 再以<br\s*?/><br\s*?/> 來分割段落, 這裡的空白符就以\s*?來代替.
regex = re.compile("""
(?<= )
.*?
(?=</div>)
""", re.VERBOSE | re.DOTALL)
m = regex.search(html)
text = '\n'.join(re.split(r"<br\s*?/><br\s*?/> ", m.group().strip()))
# text = re.sub(r"<br\s*?/><br\s*?/> ", '\n', m.group().strip())
print(text)青天白日，浩浩諸峰。
悠悠鐘聲，迴盪山間。
正是清晨時分，倚天峰上，鐘聲三響，人影綽綽。
...
陳玄一身子一傾，倒在了地上。
例項二 擷取 Python 指令碼內所有的 class 定義及其文件字串
這裡以 tkinter 庫的 __init__.py 為例
- 讀取檔案內容
import re
import pathlib
import tkinter
base = tkinter.__path__[0]
path = pathlib.Path(base).joinpath('__init__.py')
with open(path, 'rt') as f:
script = f.read()- 定義 class 的樣式
# class xxx (yyy) : """zzz"""
class_pattern = r'''
\bclass # begin of a word
\s+? # space
[\w]+? # identifier xxx
\s*? # space
( # group 1
\( # (
.*? # yyy
\) # )
)? # group 1 may not exist
\s*? # space
: # :
( # group 2
\s*? # space
(["]{3}|[']{3}) # group 3, DOC-STRING
.*? # zzz
\3 # same as group 3
)? # maybe no DOC-STRING
'''
class_regex = re.compile(class_pattern, re.VERBOSE | re.DOTALL)- 擷取內容
class_regex = re.compile(class_pattern, re.VERBOSE | re.DOTALL)
classes = [m.group() for m in class_regex.finditer(script)]
for c in classes:
print(c)class EventType(str, enum.Enum):
class Event:
"""Container for the properties of an event.
Instances of this type are generated if one of the following events occurs:
KeyPress, KeyRelease - for keyboard events
ButtonPress, ButtonRelease, Motion, Enter, Leave, MouseWheel - for mouse events
Visibility, Unmap, Map, Expose, FocusIn, FocusOut, Circulate,
Colormap, Gravity, Reparent, Property, Destroy, Activate,
Deactivate - for window events.
If a callback function for one of these events is registered
using bind, bind_all, bind_class, or tag_bind, the callback is
called with an Event as first argument. It will have the
following attributes (in braces are the event types for which
the attribute is valid):
serial - serial number of event
num - mouse button pressed (ButtonPress, ButtonRelease)
focus - whether the window has the focus (Enter, Leave)
height - height of the exposed window (Configure, Expose)
width - width of the exposed window (Configure, Expose)
keycode - keycode of the pressed key (KeyPress, KeyRelease)
state - state of the event as a number (ButtonPress, ButtonRelease,
Enter, KeyPress, KeyRelease,
Leave, Motion)
state - state as a string (Visibility)
time - when the event occurred
x - x-position of the mouse
y - y-position of the mouse
x_root - x-position of the mouse on the screen
(ButtonPress, ButtonRelease, KeyPress, KeyRelease, Motion)
y_root - y-position of the mouse on the screen
(ButtonPress, ButtonRelease, KeyPress, KeyRelease, Motion)
char - pressed character (KeyPress, KeyRelease)
send_event - see X/Windows documentation
keysym - keysym of the event as a string (KeyPress, KeyRelease)
keysym_num - keysym of the event as a number (KeyPress, KeyRelease)
type - type of the event as a number
widget - widget in which the event occurred
delta - delta of wheel movement (MouseWheel)
"""
class Variable:
"""Class to define value holders for e.g. buttons.
Subclasses StringVar, IntVar, DoubleVar, BooleanVar are specializations
that constrain the type of the value returned from get()."""
...
class LabelFrame(Widget):
"""labelframe widget."""
class PanedWindow(Widget):
"""panedwindow widget."""
例項三 字串內容轉換成資料列表
- 例如我們有一筆有關參考文獻的內容如下
import re
text = ''.join("""
[1] ShijunWangRonald M.Summe, Medical Image Analysis, Volume
16, Issue 5, July 2012, pp. 933-951 https://www.sciencedirect.
com/science/article/pii/S1361841512000333
[2] Dupuytren’s contracture, By Mayo Clinic Staff, https://
www.mayoclinic.org/diseases-conditions/dupuytrenscontracture/
symptoms-causes/syc-20371943
[3] Mean and standard deviation. http://www.bmj.com/about-bmj/
resources-readers/
publications/statistics-square-one/2-
mean-and-standard-deviation
[4] Interquartile Range IQR http://www.mathwords.com/i/
interquartile_range.htm
[5] Why are tree-based models robust to outliers? https://www.
quora.com/Why-are-tree-
based-models-robustto-
outliers
[6] https://www.dummies.com/education/math/statistics/howto-
interpret-a-correlation-coefficient-r/
[7] https://www.medicalnewstoday.com/releases/11856.php
[8] Scikit Learn Auc metrics: http://scikit-learn.org/stable/
modules/generated/sklearn.metrics.auc.html
[9] Scikit Learn Library RoC and AUC scores: http://
scikit-learn.
org/stable/modules/generated/sklearn.metrics.roc_auc_
score.html
""".strip().splitlines())- 我們要的是分開的編號, 說明及網址, 在此已經將各行都合併在一起了.
regex = re.compile(r"""
\[ # [
(\d+?) # integer
] # ]
\s+? # at least one space or more
(.*?) # any characters
\s*? # maybe no space or more
(https?://.+?) # simple http(s) match
(?=\[|$) # end with '[' or end of string, not included
""", re.VERBOSE | re.DOTALL)
for lst in regex.findall(text):
print('\n'.join(lst))- 因為我們要的結果是個列表, 所以呼叫的是
findall函式; 為了列印出來, 方便觀看, 所以又把它們分行了.
1
ShijunWangRonald M.Summe, Medical Image Analysis, Volume16, Issue 5, July 2012, pp. 933-951
https://www.sciencedirect.com/science/article/pii/S1361841512000333
2
Dupuytren’s contracture, By Mayo Clinic Staff,
https://www.mayoclinic.org/diseases-conditions/dupuytrenscontracture/symptoms-causes/syc-20371943
3
Mean and standard deviation.
http://www.bmj.com/about-bmj/resources-readers/publications/statistics-square-one/2-mean-and-standard-deviation
4
Interquartile Range IQR
http://www.mathwords.com/i/interquartile_range.htm
5
Why are tree-based models robust to outliers?
https://www.quora.com/Why-are-tree-based-models-robustto-outliers
6
https://www.dummies.com/education/math/statistics/howto-interpret-a-correlation-coefficient-r/
7
https://www.medicalnewstoday.com/releases/11856.php
8
Scikit Learn Auc metrics:
http://scikit-learn.org/stable/modules/generated/sklearn.metrics.auc.html
9
Scikit Learn Library RoC and AUC scores:
http://scikit-learn.org/stable/modules/generated/sklearn.metrics.roc_auc_score.html本作品採用《CC 協議》，轉載必須註明作者和本文連結