P38 - Python philosophy
Open Python shell, enter import this, see the following words:
The Zen of Python, by Tim Peters
Beautiful is better than ugly. Ugly rather than beautiful (Python to write beautiful code for the target)
Explicit is better than implicit. Obscure appreciated better than (the code should be beautiful and clear, naming, similar to the style)
Simple is better than complex. Simple is better than complex (beautiful code should be simple, not complex internal implementation)
Complex is better than complicated. Complex rather than messy (if complexity is inevitable, and that the code can not have inter-relationships difficult to understand, to keep the interface simple)
Flat is better than nested. Nesting rather than flat (beautiful code should be flat and not have too much nested)
Sparse is better than dense. Interval better than compact (beautiful code appropriate intervals, do not expect a line of code to solve the problem)
Readability counts. Readability is very important (beautiful code is readable)
Special cases are not special enough to break the rules. Even a special case under the guise of the name of practicality, can not be contrary to these rules (the rules supreme)
. Although practicality beats purity not all inclusive wrong, unless you are sure need to do (precisely catch the exception, do not write except: pass code style)
Errors should never pass silently. Errors should not be ignored silent
Unless explicitly silenced. Unless explicitly silence
In the face of ambiguity, refuse the temptation to guess. When there are multiple possible, do not try to guess
There should be one—— and preferably only one ——obvious way to do it.而是尽量找一种，最好是唯一一种明显的解决方案（如果不确定，就用穷举法）
Although that way may not be obvious at first unless you're Dutch.虽然这并不容易，因为你不是 Python 之父（这里的 Dutch 是指 Guido ）
Now is better than never.现在做总比不做好
Although never is often better than "right" now.尽管过去从未比现在好
If the implementation is hard to explain , it's a bad idea.做也许好过不做，但不假思索就动手还不如不做（动手之前要细思量）
If the implementation is easy to explain, it may be a good idea.如果你无法向人描述你的方案，那肯定不是一个好方案；反之亦然（方案测评标准）
Namespaces are one honking great idea —— let's do more of those!命名空间是一种绝妙的理念，我们应当多加利用（倡导与号召）
P40——print打印
通配符的使用
# %s 只能打印字符串
name = "zhangsan"
print("hello, %s" %name)
# %d 只能打印数字
number = 10
print("Number is %d" %number)
# %r 打印任意类型
n = 100
print("You print is %r ." %n)
input输入，在Python2中为了避免读取非字符串类型可能发生的错误，使用raw_input()代替input()
n = input("Enter any content:")
print ("Your input is %r " %n)
P43——分支与循环
if 语句
a = 2
b = 3
if a > b:
print("a max!")
else:
print("b max!")
in和not In
alphabet = "abc"
if "a" in alphabet:
print("Contain")
else:
print("Not Contain")
if_elif_elif_else
results = 72
if results >=90:
print("优秀")
elif results >=70:
print("良好")
elif results >=60:
print("及格")
else:
print("不及格")
for语句
打印字符信息
for i in "Hello world":
print(i)
打印数组信息
fruits = ['banana','apple','mango']
for fruit in fruits:
print(fruit)
rang()函数从零开始循环，range(start,end,[,step]),start开始位置，end结束位置，step循环间隔
for i in rang(5):
print(i)
P47——数组和字典
数组
lists = [1,2,'c',4]
# 显示所有数组信息
lists
# 显示对应下标元素信息
lists[0]
# 修改对应下标元素信息
lists[1] = 'b'
# 想数组末尾增加数组元素
lists.append('5')
字典
dict = {"userName":"zhangsan","password":123}
# 获取键信息列表
dict.keys()
# 获取所有值信息列表
dict.values()
# 将所有的字典项以键值对列表方式返回
dict.items()
P49——函数、类、方法
函数
def add(a,b):
print(a+b)
add(2,5)
def add(a,b):
return a + b
add(2,3)
def add(a=1,b=5):
return a + b
add()
类和方法
init初始化方法重构
class sum():
def _init_(self,a,b):
self.a = int(a)
self.b = int(b)
def add(self):
return self.a + self.b
count = sum('2',4)
print(count.add())
引用第三方库
help(time)查看类库的说明
import time
print(time.ctime())
from time import ctime
print(time.ctime())
from time import *
print(time.ctime())
P56——跨目录调用模块，在Python2中需要创建一个_init_.py文件
import sys
sys.path.append("./model") # 将model目录添加到系统环境变量path下
from model import new_count
test = new_count.B()
test.add(2,4)
P60——异常