Python-语法模板大全(常用)

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

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))

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)

# 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}

4.1. 列表生成器

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

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

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')

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