常用正则：匹配首个数字字段，输出123

import re

txt = "abc123def456ghi789jkl333"
patternNum = '[0-9]+'
obj = re.search(patternNum, txt)
print(obj.group())

常用正则：匹配所有数字字段，输出['123', '456', '789', '333']

import re

txt = "abc123def456ghi789jkl333"
patternAllNum = '[0-9]+'
res = re.findall(patternNum, txt)
print(res)

---------------------
import re

txt = "abc123def456ghi789jkl3333"
patternAllNum = re.compile('[0-9]+')
res = patternAllNum.findall(txt)
print(res)  # ['123', '456', '789', '3333']

常用正则：匹配两个特殊符号之间的所有内容，输出['123', 'jkl', '哈哈哈', '呵呵呵']

import re

txt = "abc#123#def456ghi789#jkl#333#哈哈哈##呵呵呵#"
patternTopic = re.compile(r"\#(.+?)\#")
res = patternTopic.findall(txt)
print(res)

常用正则：删除（用”“替换）两个特殊符号之间的所有内容，输出abcdefghijkl

import re

txt = "abc[123]def[456]ghi[789]jkl[333]"
txt = re.sub(r"\[(.+?)\]", "", txt) 
print(txt)

常用正则：发现微博用户，在@之后，空格之前。或者@之后到文本结束标识，输出['高校联盟', '复旦大学', '北大']

import re

txt = '''
哈哈哈，呵呵呵，嘿嘿嘿。@高校联盟 @复旦大学 @北大
'''
print(txt)
patternUsers = re.compile(r'@([\u4e00-\u9fa5\w\-]+)')
res = patternUsers.findall(txt)
print(res)