import re
 
text = "123h1ello world"
text1 = "123Hello world456"
text2 = "hello world"
 
res = re.match("\d*", text)  
res1 = re.match("\d*", text1)
res2 = re.match("\d*", text2)
 
print(res.group())
print(res1.group())
print(res2.group())

import re
#注意是前一个字符
ret = re.match("[A-Z][a-z]*","M")
print(ret.group())

ret = re.match("[A-Z][a-z]*","AaBcDE")
print(ret.group())

ret = re.match("[A-Z][a-z]*","Aabcdef")
print(ret.group())

import re
 
text = "he+llo world"
text1 = "Hello world456"
text2 = "+hello world"
 
res = re.match("\w+", text)
res1 = re.match("\w+", text1)
res2 = re.match("\w+", text2)
 
print(res.group())
print(res1.group())
print(res2)

import re
names = ["name1","_name","2_name","__name__"]
for i in names:
  ret = re.match("[a-zA-Z_]+[\w]*",i)
  if ret:
    print("变量名 %s 符合要求" % ret.group())
  else:
    print("变量名 %s 非法" % i)

import re
 
text = "he+llo world"
text1 = "Hello world456"
text2 = "hello world"
 
res = re.match("\w{2}", text)
res1 = re.match("\w{3}", text1)
res2 = re.match("\w{4}", text2)
 
print(res.group())
print(res1.group())
print(res2.group())

import re
ret = re.match("[a-zA-Z0-9_]{6}","123a3g45678")
print(ret.group())

ret = re.match("[[a-zA-Z0-9_]{8,20}","1ad3123456addfcasdef")
print(ret.group())

import re
 
text = "hello world"
text1 = "Helloworld456"
text2 = "hello world"
 
res = re.match("\w{2,5}", text)
res1 = re.match("\w{6,8}", text1)
res2 = re.match("\w{20,25}", text2)
 
print(res.group())
print(res1.group())
print(res2)