Python-语法模板大全(常用)

• 2020 年 1 月 19 日
• 笔记

目录

• 1.怎么存数据
  • 变量:
  • 字符串: 不可变对象
  • 列表:
  • 元组:
  • 字典:
  • 三大容器的遍历方法
• 2.怎么用数据
  • 数字操作符：
  • 判断循环:
• 3.函数
• 4. Python核心编程
  • 4.1. 列表生成器
• 5. 类和对象
  • 5.1. 定义类的模板
  • 5.2.继承
  • 5.3 多态
• 6. IO文件操作和OS目录操作
  • OS操作
  • IO文件
• 7. 正则表达式及re模块的使用
  • 7.2. re模块的使用

1.怎么存数据

插入Python数据类型.png

变量:

age =10

字符串: 不可变对象

name = "python"

a = "pythonpythonpython"    # 索引和切片  a[0]         # index  a[-1]  a[0:3]       # slice  a[0:6:2]  a[-1:-7:-1]  a[::-1]          # slice reverse

字符串方法详见：https://www.cnblogs.com/haochen273/p/10244032.html#%E5%AD%97%E7%AC%A6%E4%B8%B2

列表:

[1,2,3,"python"]

a = [1,2,3,"python"]    len(a)  a[0]  [i*2 for i in a]  a.append(50)  a.insert(2,15)  a.extend([5,8,10])  a[0]="java"  "python" in a  a.index("python")  a.count(1)  a.pop(index)

元组:

(1,2,3)（不可以更改.与list类似）

字典:

{"a":100, "b":"666"}

d = {'Michael': 95, 'Bob': 75, 'Tracy': 85}    d['Michael']  d['Adam'] = 67  'Thomas' in d  d.get('Thomas')  d.pop('Bob')

三大容器的遍历方法

a = [1,2,3]  for i in a:      print(i)    b = (1,2,3)  for i in b:      print(b)    c = {"a":10, "b":20, "c":30}  for key,value in dict.items():      print("key = %s, value = %d"%(key,value))

2.怎么用数据

数字操作符：

+、-、*、/、%、//、**

判断循环:

• if判断:

if a>10:    b = a + 20    if b>20:      pass  elif: a>8:    pass  else:    pass

• while循环

while i<5:    # do something    pass    i = i + 1    while true:    pass

• for循环

for i in [1,2,3]:      print(i) 

• break和continue的使用

# break:打断全部循环  for i in [1,2,3,4,5]:      print("----")      if i==4:          break      print(i)  # continue： 打断一次循环  for i in [1,2,3,4,5]:      print("----")      if i==4:          continue      print(i)

3.函数

# 位置参数  def person(name, age):    print(name,age)    # 默认参数    def person(name,age=20):    print(name, age)    # 关键字参数  def person(name, age, **kw):      print('name:', name, 'age:', age, 'other:', kw)    person('hao', 20) # name: Michael age: 30 other: {}  person('hao', 20, gener = 'M', job = 'Engineer') # name: Adam age: 45 other: {'gender': 'M', 'job': 'Engineer'}  extra = {'city': 'Beijing', 'job': 'Engineer'}  person('Jack', 24, **extra)    # 命名关键字参数  def person(name, age, *, city='Beijing', job):      print(name, age, city, job)    person('Jack', 24, job = '123')  person('Jack', 24, city = 'Beijing', job = 'Engineer')    # Combination  # 可变 + 关键字参数  def f1(a, b, c=0, *args, **kw):      print('a =', a, 'b =', b, 'c =', c, 'args =', args, 'kw =', kw)    f1(1, 2, 3, 'a', 'b')   # a = 1 b = 2 c = 3 args = ('a', 'b') kw = {'x': 99}  f1(1, 2, 3, 'a', 'b', x=99) # a = 1 b = 2 c = 0 d = 99 kw = {'ext': None}    # 默认参数 + 命名关键字参数 + 关键字参数  def f2(a, b, c=0, *, d, **kw):      print('a =', a, 'b =', b, 'c =', c, 'd =', d, 'kw =', kw)    f2(1, 2, d=99, ext=None) # a = 1 b = 2 c = 0 d = 99 kw = {'ext': None}

4. Python核心编程

4.1. 列表生成器

[x * x for x in range(1, 11) if x % 2 == 0]

5. 类和对象

5.1. 定义类的模板

class Student(object):      def __init__(self, name, score):          self.__name = name          self.__score = score        # print(mike)      def __str__(self):          msg = "name: " + self.__name + "score: " + str(self.__score)          return msg        # mike      __repr__ = __str__      # mike()      __call__ = __str__        @property      def name(self):          return self.__name        @name.setter      def name(self, value):          if type(value) == str:              self.__name = value          else:              raise ValueError('Bad name')        @property      def score(self):          return self.__score        @score.setter      def score(self, value):          if 0 <= value <= 100:              self.__score = value          else:              raise ValueError('Bad score')        def final_report(self):          if self.__score >= 90:              level = 'A'          elif self.__score >= 70:              level = 'B'          elif self.__score >= 60:              level = 'C'          else:              level = 'D'          msg = "Your final value is: " + level          return msg    # 调用    mike = Student('mike', 85)  print("-" * 20 + "Print property" + "-" * 20)  print(mike)  print("name: %s" % (mike.name))  print("-" * 30 + "Print methods" + "-" * 20)  print(mike.final_report())  print("-" * 30 + "Print modified infor" + "-" * 20)  mike.name = "Obama"  mike.score = 50  print("-" * 30)  print("modified name: %s" % (mike.name))

--------------------Print property--------------------  name: mikescore: 85  name: mike  ------------------------------Print methods--------------------  Your final value is: B  ------------------------------Print modified infor--------------------  ------------------------------  modified name: Obama

5.2.继承

class SixGrade(Student):      def __init__(self, name, score, grade):          super().__init__(name, score)          self.__grade = grade        # grade是一个只读属性      @property      def grade(self):          return self.__grade        def final_report(self, comments):          # 子类中调用父类方法          text_from_Father = super().final_report()          print(text_from_Father)          msg = "commants from teacher: " + comments          print(msg)    print("-" * 20 + "继承" + "-" * 20)  fangfang = SixGrade('fang', 95, 6)  fangfang.final_report("You are handsome")  print(fangfang.grade)

--------------------继承--------------------  Your final value is: A  commants from teacher: You are handsome  6

5.3 多态

class SixGrade(Student):      pass    class FiveGrade(Student):      pass    def print_level(Student):      msg = Student.final_report()      print(msg)    print_level(Student('from class', 90))  print_level(SixGrade('from subclass-1', 56))  print_level(FiveGrade('from subclass-2', 85))

Your final value is: A  Your final value is: D  Your final value is: B

6. IO文件操作和OS目录操作

OS操作

import os  # 获取当前目录的绝对路径  path = os.path.abspath('.')  # 创建一个目录  os.path.join('/Users/michael', 'testdir')  os.mkdir('/Users/michael/testdir')  # 删除一个目录  os.rmdir('/Users/michael/testdir')  # 拆分路径  os.path.split('/Users/michael/testdir/file.txt')  # ('/Users/michael/testdir', 'file.txt')  os.path.splitext('/path/to/file.txt')  # ('/path/to/file', '.txt')  # 重命名  os.rename('test.txt', 'test.py')  # 删除文件  os.remove('test.py')  # 列出所有python文件  [x for x in os.listdir('.') if os.path.isfile(x) and os.path.splitext(x)[1]=='.py']

IO文件

# 读    # 下面是read()方法的使用，“r”表示read  with open('testRead.txt', 'r', encoding='UTF-8') as f1:      results = f1.read()    # 读取数据      print(results)    # 下面是readline()方法的使用，“r”表示read  with open('testRead.txt', 'r', encoding='UTF-8') as f2:      line = f2.readline()    # 读取第一行      while line is not None and line != '':          print(line)          line = f2.readline()    # 读取下一行    # 下面是readlines()方法的使用，“r”表示read  with open('testRead.txt', 'r', encoding='UTF-8') as f3:      lines = f3.readlines()    # 接收数据      for line in lines:     # 遍历数据          print(line)    # 写    with open('/User/test.txt', 'w') as f:    f.write('hello')

7. 正则表达式及re模块的使用

主要参考资料为：

• Python正则表达式指南 6.1. 正则表达式语法
• re模块的使用

7.2. re模块的使用

内置的 re 模块来使用正则表达式，提供了很多内置函数：

1. pattern = re.compile(pattern[, flag]):

• 参数：
  • pattern: 字符串形式的正则
  • flag: 可选模式，表示匹配模式
• 例子：

import re    pattern = re.compile(r'd+')

1. Pattern的常用方法

import re    pattern = re.compile(r'd+')    m0 = pattern.match('one12twothree34four')  m = pattern.match('one12twothree34four', 3, 10)    print("-" * 15 + "Match methods" + "-" * 15)  print("found strings: ", m.group(0))  print("start index of found strings: ", m.start(0))  print("end index of found strings: ", m.end(0))  print("Span length of found strigns: ", m.span(0))    s = pattern.search('one12twothree34four')    print("-" * 15 + "Search methods" + "-" * 15)  print("found strings: ", s.group(0))  print("start index of found strings: ", s.start(0))  print("end index of found strings: ", s.end(0))  print("Span length of found strigns: ", s.span(0))    f = pattern.findall('one1two2three3four4', 0, 10)    print("-" * 15 + "findall methods" + "-" * 15)  print("found strings: ", f)    f_i = pattern.finditer('one1two2three3four4', 0, 10)    print("-" * 15 + "finditer methods" + "-" * 15)  print("type of method: ", type(f_i))  for m1 in f_i:  # m1 是 Match 对象      print('matching string: {}, position: {}'.format(m1.group(), m1.span()))    p = re.compile(r'[s,;]+')  print("-" * 15 + "Split methods" + "-" * 15)  print("split a,b;c.d: ", p.split('a,b;; c   d'))    p1 = re.compile(r'(w+) (w+)')  s1 = 'hello 123, hello 456'      def func(m):      return 'hi' + ' ' + m.group(2)      print("-" * 15 + "替换 methods" + "-" * 15)  print(p1.sub(r'hello world', s1))  # 使用 'hello world' 替换 'hello 123' 和 'hello 456'  print(p1.sub(r'2 1', s1))  # 引用分组  print(p1.sub(func, s1))  print(p1.sub(func, s1, 1))  # 最多替换一次

结果是:

---------------Match methods---------------  found strings:  12  start index of found strings:  3  end index of found strings:  5  Span length of found strigns:  (3, 5)  ---------------Search methods---------------  found strings:  12  start index of found strings:  3  end index of found strings:  5  Span length of found strigns:  (3, 5)  ---------------findall methods---------------  found strings:  ['1', '2']  ---------------finditer methods---------------  type of method:  <class 'callable_iterator'>  matching string: 1, position: (3, 4)  matching string: 2, position: (7, 8)  ---------------Split methods---------------  split a,b;c.d:  ['a', 'b', 'c', 'd']  ---------------替换 methods---------------  hello world, hello world  123 hello, 456 hello  hi 123, hi 456  hi 123, hello 456