python中正则表达式的使用方法

a = 'xy123'
b = re.findall('x...',a)
print(b)
# ['xy12']

a = 'xyxy123'
b = re.findall('x*',a)
print(b)
# ['x', '', 'x', '', '', '', '', '']

a = 'xy123'
b = re.findall('x?',a)
print(b)
# ['x', '', '', '', '', '']

b = re.findall('xx.*xx',secret_code)
print(b)
# ['xxIxxfasdjifja134xxlovexx23345sdfxxyouxx']

c = re.findall('xx.*?xx',secret_code)
print(c)
# ['xxIxx', 'xxlovexx', 'xxyouxx']

d = re.findall('xx(.*?)xx',secret_code)
print(d)
for each in d:
  print(each)
# ['I', 'love', 'you']
# I
# love
# you

s = '''sdfxxhello
xxfsdfxxworldxxasdf'''

d = re.findall('xx(.*?)xx',s,re.S)
print(d)
# ['hello\n', 'world']

s2 = 'asdfxxIxx123xxlovexxdfd'
f = re.search('xx(.*?)xx123xx(.*?)xx',s2).group(2)
print(f)
f2 = re.findall('xx(.*?)xx123xx(.*?)xx',s2)
print(f2[0][1])
# love
# love

s = '123rrrrr123'
output = re.sub('123(.*?)123','123%d123'%789,s)
print(output)
# 123789123

import re

def multiply(m):
  # Convert group 0 to an integer.
  v = m.group(0)
  print(v)
  # Multiply integer by 2.
  # ... Convert back into string and return it.
  print('basic/'+v)
  return 'basic/'+v

>>>autoencoder.png
  basic/autoencoder.png
  RNN.png
  basic/RNN.png
  rnn_step_forward.png
  basic/rnn_step_forward.png
  rnns.png
  basic/rnns.png
  rnn_cell_backprop.png
  basic/rnn_cell_backprop.png
  LSTM.png
  basic/LSTM.png
  LSTM_rnn.png
  basic/LSTM_rnn.png
  attn_mechanism.png
  basic/attn_mechanism.png
  attn_model.png
  basic/attn_model.png

import re

def add(m):
  # Convert.
  v = int(m.group(0))
  # Add 2.
  return str(v + 1)

# Call re.subn.
result = re.subn("\d+", add, "1 2 3 4 5")

print("Result string:", result[0])
print("Number of substitutions:", result[1])
>>>
Result string: 11 21 31 41 51
Number of substitutions: 5