淺談Python中re.match()和re.search()的使用及區(qū)別

更新時(shí)間：2020年04月14日 16:14:09 作者：SpiderLiH

這篇文章主要介紹了淺談Python中re.match()和re.search()的使用及區(qū)別，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。一起跟隨小編過來看看吧

1.re.match()

re.match（）的概念是從頭匹配一個(gè)符合規(guī)則的字符串，從起始位置開始匹配，匹配成功返回一個(gè)對(duì)象，未匹配成功返回None。

包含的參數(shù)如下：

pattern：正則模型

string ：要匹配的字符串

falgs ：匹配模式

match() 方法一旦匹配成功，就是一個(gè)match object對(duì)象，而match object對(duì)象有以下方法：

group() 返回被 RE 匹配的字符串

start() 返回匹配開始的位置

end() 返回匹配結(jié)束的位置

span()返回一個(gè)元組包含匹配 (開始,結(jié)束) 的位置

案例：

import re
# re.match 返回一個(gè)Match Object 對(duì)象
# 對(duì)象提供了 group() 方法，來獲取匹配的結(jié)果
result = re.match("hello","hello,world")
if result:
  print(result.group())
else:
  print("匹配失敗!")

輸出結(jié)果：

hello

2.re.search()

re.search（）函數(shù)會(huì)在字符串內(nèi)查找模式匹配,只要找到第一個(gè)匹配然后返回，如果字符串沒有匹配，則返回None。

格式：re.search(pattern, string, flags=0)

要求：匹配出文章閱讀的次數(shù)

import re

ret = re.search(r"\d+", "閱讀次數(shù)為 9999")
print(ret.group())

輸出結(jié)果：

9999

3.match()和search()的區(qū)別：

match（）函數(shù)只檢測(cè)RE是不是在string的開始位置匹配，

search()會(huì)掃描整個(gè)string查找匹配

match（）只有在0位置匹配成功的話才有返回，如果不是開始位置匹配成功的話，match()就返回none

舉例說明：

import re
print(re.match('super', 'superstition').span())

(0, 5)

print(re.match('super','insuperable'))

None

print(re.search('super','superstition').span())

(0, 5)

print(re.search('super','insuperable').span())

(2, 7)

補(bǔ)充知識(shí)： jupyter notebook_主函數(shù)文件如何調(diào)用類文件

使用jupyter notebook編寫python程序，rw_visual.jpynb是寫的主函數(shù)，random_walk.jpynb是類（如圖）。在主函數(shù)中將類實(shí)例化后運(yùn)行會(huì)報(bào)錯(cuò)，經(jīng)網(wǎng)絡(luò)查找解決了問題，缺少Ipynb_importer.py這樣一個(gè)鏈接文件。

解決方法：

1、在同一路徑下創(chuàng)建名為Ipynb_importer.py的文件：File-->download as-->Python(.py)，該文件內(nèi)容如下：

#!/usr/bin/env python
# coding: utf-8
# In[ ]:
 
import io, os,sys,types
from IPython import get_ipython
from nbformat import read
from IPython.core.interactiveshell import InteractiveShell
 
class NotebookFinder(object):
  """Module finder that locates Jupyter Notebooks"""
  def __init__(self):
    self.loaders = {}
 
  def find_module(self, fullname, path=None):
    nb_path = find_notebook(fullname, path)
    if not nb_path:
      return
 
    key = path
    if path:
      # lists aren't hashable
      key = os.path.sep.join(path)
 
    if key not in self.loaders:
      self.loaders[key] = NotebookLoader(path)
    return self.loaders[key]
 
def find_notebook(fullname, path=None):
  """find a notebook, given its fully qualified name and an optional path
  This turns "foo.bar" into "foo/bar.ipynb"
  and tries turning "Foo_Bar" into "Foo Bar" if Foo_Bar
  does not exist.
  """
  name = fullname.rsplit('.', 1)[-1]
  if not path:
    path = ['']
  for d in path:
    nb_path = os.path.join(d, name + ".ipynb")
    if os.path.isfile(nb_path):
      return nb_path
    # let import Notebook_Name find "Notebook Name.ipynb"
    nb_path = nb_path.replace("_", " ")
    if os.path.isfile(nb_path):
      return nb_path
 
class NotebookLoader(object):
  """Module Loader for Jupyter Notebooks"""
  def __init__(self, path=None):
    self.shell = InteractiveShell.instance()
    self.path = path
 
  def load_module(self, fullname):
    """import a notebook as a module"""
    path = find_notebook(fullname, self.path)
 
    print ("importing Jupyter notebook from %s" % path)
 
    # load the notebook object
    with io.open(path, 'r', encoding='utf-8') as f:
      nb = read(f, 4)
 
 
    # create the module and add it to sys.modules
    # if name in sys.modules:
    #  return sys.modules[name]
    mod = types.ModuleType(fullname)
    mod.__file__ = path
    mod.__loader__ = self
    mod.__dict__['get_ipython'] = get_ipython
    sys.modules[fullname] = mod
 
    # extra work to ensure that magics that would affect the user_ns
    # actually affect the notebook module's ns
    save_user_ns = self.shell.user_ns
    self.shell.user_ns = mod.__dict__
 
    try:
     for cell in nb.cells:
      if cell.cell_type == 'code':
        # transform the input to executable Python
        code = self.shell.input_transformer_manager.transform_cell(cell.source)
        # run the code in themodule
        exec(code, mod.__dict__)
    finally:
      self.shell.user_ns = save_user_ns
    return mod
sys.meta_path.append(NotebookFinder())

2、在主函數(shù)中import Ipynb_importer

import matplotlib.pyplot as plt
import Ipynb_importer
 
from random_walk import RandomWalk
 
rw = RandomWalk()
rw.fill_walk()
plt.scatter(rw.x_values, rw.y_values, s=15)
plt.show()

3、運(yùn)行主函數(shù)，調(diào)用成功

ps:random_walk.jpynb文件內(nèi)容如下：

from random import choice
 
class RandomWalk():
  def __init__(self, num_points=5000):
    self.num_points = num_points
    self.x_values = [0]
    self.y_values = [0]
    
  def fill_walk(self):
    while len(self.x_values) < self.num_points:
      x_direction = choice([1,-1])
      x_distance = choice([0,1,2,3,4])
      x_step = x_direction * x_distance
      
      y_direction = choice([1,-1])
      y_distance = choice([0,1,2,3,4])
      y_step = y_direction * y_distance
      
      if x_step == 0 and y_step == 0:
        continue
        
      next_x = self.x_values[-1] + x_step
      next_y = self.y_values[-1] + y_step
      
      self.x_values.append(next_x)
      self.y_values.append(next_y)

運(yùn)行結(jié)果：