Python Day02

• 模块

sys

import sys

print(sys.path)
print(sys.argv)

os

import os

os.system("dir")
cmd_res = os.popen("dir").read()
print(cmd_res)

• pyc
• 数据类型

1.int 在Python中整型数据超过边界后不会报错，类型会变为long，但是在C#中会报错

#32位
type(2*30)
==>int
type(2*31)
==>long

#64位
type(2*62)
==>int
type(2**63)
==>long

2.long 在Python中长整型没有数值的大小

3.float 占8个字节(64位)，其中52位表示底，11位表示指数，剩下1位表示符号

4.bool

5.string

• 三元运算

a,b,c = 1,3,5

d = a if a > b else c
==>d = 5

• 进制
• 编码解码

各类型转二进制 encode相反为decode 类似C#(Encoding.Default.GetBytes(str)/Encoding.Defalut.GetString(Bytes)

msg = "陕西西安"
# print(msg.encode()) 因为本是为UTF8所以windows下不会报错但是Linux会
print(msg.encode("utf-8"))
print(msg.encode(encoding="utf-8"))
print(msg.encode(encoding="utf-8").decode(encoding="utf-8"))

======================================================
b'\xe9\x99\x95\xe8\xa5\xbf\xe8\xa5\xbf\xe5\xae\x89'
b'\xe9\x99\x95\xe8\xa5\xbf\xe8\xa5\xbf\xe5\xae\x89'
陕西西安
=======================================================

• List

names = ["XiYangyang", "NuanYangyang", "MeiYangyang","LanYangyang","LanYangyang"]
print(names[0])
=> XiYangyang

# 打印区间
print(names[0:3])
=>["XiYangyang", "NuanYangyang", "MeiYangyang"]

# 从右边打印一个
print(names[-1])
=>LanYangyang

# 打印右边2个
print(names[-1:-3]
=>['NuanYangyang', 'MeiYangyang']

# 打印后三个
print(names[-3:])
=>['NuanYangyang', 'MeiYangyang', 'LanYangyang']

# 追加
names.append("HuiTailang")
print(names)
=>['XiYangyang', 'NuanYangyang', 'MeiYangyang', 'LanYangyang', 'HuiTailang']

# 指定位置插入
names.insert(0,"HongTailang")
print(names)
=>['HongTailang', 'XiYangyang', 'NuanYangyang', 'MeiYangyang', 'LanYangyang', 'HuiTailang']

names[0] = "ManYangyang"
print(names)
=>['ManYangyang', 'XiYangyang', 'NuanYangyang', 'MeiYangyang', 'LanYangyang', 'HuiTailang']

# 删除
names.remove("ManYangyang") #del names[0]
prints(names)
=>['XiYangyang', 'NuanYangyang', 'MeiYangyang', 'LanYangyang', 'HuiTailang']

# 弹出一个元素 如果不指定位置则弹出最后一位
popname = names.pop()#names.pop(0)
print(names,popname)
=>['XiYangyang', 'NuanYangyang', 'MeiYangyang', 'LanYangyang'] HuiTailang

# 元素在list中的位置
print(names.index("NuanYangyang"))
=>1

# 元素在list中总个数
names = ["XiYangyang", "NuanYangyang", "MeiYangyang","LanYangyang","LanYangyang"]
print(names.count("LanYangyang"))
=>2

# 方向排列
names.reverse()
print(names)
=>['LanYangyang', 'LanYangyang', 'MeiYangyang', 'NuanYangyang', 'XiYangyang']

# 排序
names.sort()
print(names)
=>['LanYangyang', 'LanYangyang', 'MeiYangyang', 'NuanYangyang', 'XiYangyang']

# 延伸
names2 = [1,2,3]
names.extend(names2)
print(names)
=>['LanYangyang', 'LanYangyang', 'MeiYangyang', 'NuanYangyang', 'XiYangyang', 1, 2, 3]

names.clear()
=>[]