# 本文目的：总览 Python 的主要语法，并供日后备忘。
# 阅读指南：本文不是文档。通过通读本文，可以了解 Python 基本的语法及一些常用的方法。读者可以将其与其他语言比较，理解其意图与含义。
# 目标读者：具有程序设计基础知识，理解面向对象程序设计基本概念的程序员。
# 若使用 Python 2.X，需设定字符编码以支持中文字符
# -*- coding: UTF-8 -*-
# coding=utf-8
# 模块导入
from math import pi, sqrt # 同时导入多个模块
from re import match as re_match # 重命名
# 类的定义与继承
class Animal:
__character = "Positive" # 不会经过 "from module_name import *" 导入
_gender = "Unknown" # 仅表示建议不访问
"""
文档注释，将在运行时输出
"""
def __init__(self, name, age):
self.name = name
self.age = age
def shout(self): # 定义类的方法
print("Sound")
def live(self):
print("Alive!")
def train(behavior): # 修饰器
def wrap():
behavior()
return wrap
@property # 属性，常用于实现只读特性
def gender(self):
return self._gender
@gender.setter # 实现属性的赋值
def gender(self, value):
if value:
self._gender = value
else:
print("Gender not set")
class Wolf(Animal): # 继承于 Animal 类
def shout(self, default = "Woof!", *sounds, **tones):
print(default)
if len(sounds) > 0:
print(sounds[0])
print(tones) # {'key':value,}
def bite(self):
print("Bite!")
class Dog(Wolf):
def shout(self):
print("Woo")
def bite(self):
print("Bite?")
super().shout()
def __add__(self, other): # 改写 + 运算符。其他运算符也可以类似形式改写
return Dog(self.name + " and " + other.name, self.age + other.age)
def __special_behavior(self): # 该方法不会经过 "from module_name import *" 导入
print("Read books!")
@classmethod # 定义类方法
def find_a_puppy(cls, name):
return cls(name, 0)
@staticmethod # 定义静态方法
def find(times)
print((self.name + "!") * 3)
@train
def run():
print("train running")
# 访问类
puppy = Dog("Puppy", 5)
print(puppy.age) # 5
puppy.live() # Alive!
puppy.shout() # Woo
puppy.bite() # Bite? Woof!
print(_Animal__character) # Positive
# 数组相关
def add_one(x):
return x + 1
nums = [1,2,3]
result_map = list(map(add_one,nums)) # [2,3,4]
result_filter = list(filter(lambda x:x%2==0,nums)) # [1,3]
nums[0:2:1] # [1,2,3]
nums[1:-1] # [2,3]
first = nums[0]
print(list(range(3))) # [0,1,2]
# Generator 与循环
def infinitive_loop():
i = 1
while True:
yield i
if True:
i += 1
elif False:
i = 0
else
i = 1
for i in infinitive_loop():
print(i) # 1 2 3...
if False:
break
else:
print("finished without break")
# 集合
num_set = {1,2,3}
print(3 in num_set) # True
# 字典
age_dictionary = {"Alice":17, "Bob":18}
print(age_dictionary["Alice"]
# 多元组
immutable_tuple = ("A","B") # tuple 始终无法被更改
simple_tuple = 1,2,3
a,b = immutable_tuple
a, *b, c = [1,2,3,4] # a 为 1, b 为 [2,3]，c 为 4
b = 5 if a == 2 else 3 # b 为 3
# 字符串格式
string_format_sample = "String: {0} {1} {x}".format("A","B",x="C")
# 异常处理
try:
print(1/0)
assert (2 + 2 == 6), "wrong answer" # AssertionError:wrong answer
with open("file.txt") as f:
print(f.read())
file = open(file.txt)
print("A" * 3) # AAA
n = int("9")
except ZeroDivisionError:
print("Devided by zero"
except (ValueError, TypeError):
print("Error")
finally:
file.close()
print("Finally")
raise
input("Enter a number: ")
if __name__=="__main__":
print("Won't be printed if it is imported")