Python-语法模板大全(常用)

目录

• 1.怎么存数据
• 2.怎么用数据
• 3.函数
• 4. 类和对象
• 5. io文件操作和os目录操作
• 6. 正则表达式及re模块的使用

1.怎么存数据

• 变量: age =10
• 字符串: name = "python"
• 列表: [1,2,3,"python"]
• 元组: (1,2,3)（不可以更改）
• 字典: {"a":100, "b":"666"}

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

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. 类和对象

4.1. 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

4.2.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

4.3 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

5. 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

方法	特性	性能
read()	读取全部内容	一般
readline()	每次读出一行内容	占用内存最少
readlines()	读取整个文件所有行，保存在一个列表(list)变量中，每行作为一个元素	最好(内存足)
write()	写文件

# 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')

6. 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

6.2. 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