python 学习笔记3

# li = [11,22,33,44]
# def f1(arg):
# arg.append(55)
# # li = f1(li)
# f1(li)
# print(li)


# 不太重要
# 是否可以被执行被调用
# def f1():
# pass
## f1()
# f2 = 123
## f2()
# print(callable(f1))

# print(callable(f2))
# callable()

# ascil码转换列表 相互转换对应关系
# 数字转换成字母
# r = chr(65)
# print(r)
# A

# 字母转换成数字
# n = ord("a")
# print(n)
# 97



#生成字母随机验证码
# import random
# li = []
# for i in range(6):
# temp = random.randrange(65,91)
# c = chr(temp)
# li.append(c)
# result = "".join(li)
# print(result)



# 生成随机数字
# import random
# 1 <= i <5
# i = random.randrange(1,5)
# i = random.randrange(65,91)
# c = chr(i)
# print(c)

# 生成字母
# import random
# li = []
# for i in range(6):
# temp = random.randrange(65,91)
# c = chr(temp)
# li.append(c)
# result = "".join(li)
# print(result)


#生成字母数字,随机生成数字字母
# import random
# li = []
# for i in range(6):
# if i ==2 or i ==4:
# num = random.randrange(0,10)
# li.append(str(num))
# else:
# temp = random.randrange(65,91)
# c = chr(temp)
# li.append(c)
# result = "".join(li)
# print(result)

#生成字母数字,随机生成数字字母不限制位数
# import random
# li = []
# for i in range(6):
# r = random.randrange(0,5)
# if r ==2 or r ==4:
# num = random.randrange(0,10)
# li.append(str(num))
# else:
# temp = random.randrange(65,91)
# c = chr(temp)
# li.append(c)
#
# result = "".join(li)
# print(result)


# compile()编译代码
# python s1.py
# 1、读取文件内容,str到内存
# 2、python内部,把字符串-》编译成 -》特殊代码
# 3、执行代码
# s = "print(123)"
# 编译 single(单行),eval(表达式),exec(python)
# 将字符串编译成python代码
# r = compile(s,"<string>","exec")
# print(r) #<code object <module> at 0x101b1f5d0, file "<string>", line 1>
# exec 执行python代码
# exec(r) # 123
# eval()

# 执行python代码,接收:代码或者字符串
# exec("7+8+9")
# eval 执行表达式,并获取结果
# ret = eval("7+9+8")
# print(ret)


# 执行python代码,继续接收代码或者字符串
# exec("7+9+8")
#执行表达式,并获取结果
# ret = eval("7+9+8")
# print(ret)

# 快速查看,对象提供了哪些功能
# print(dir(dict))
# 查看帮助
# help(list)


# 共:97,每页显示10条,需要多少页
# r = divmod(97,10)
# print(r) 商9 余数7
# r = divmod(100,10)
# print(r[0]) 商
# print(r[1]) 余数


# s = "alex" 对象,"alex" => str

# s = [11,11,11]
# isinstance 用于判断,对象是否是某个类的实例
# r = isinstance(s,list)
# print(r) 返回True



# filter,map

# def f1(args):
# result = []
# for item in args:
# if item > 22:
# result.append(item)
# return result
#
# li = [11,22,33,44,55]
# ret = f1(li)
# print(ret) 33,44,55


# filter (函数,可迭代的对象)
# def f2(a):
# if a > 22:
# return True
# li = [11,22,33,44,55]
# ret = filter(f2,li)
# print(list(ret))


# filter内部,循环第二个参数
# result = []
# for item in 第二个参数
# r = 第一个参数(item)
# if r:
# result(item)
# return result
# filter , 循环第二个参数,让每个循环元素执行 函数(第一个参数),如果函数返回值True,表示元素合法

# ret = filter(f2,li)
# print(list(ret))


# 自动return
# f1 = lambda a: a >30
# ret = f1(90)
# print(ret) True

# filter 函数返回True,将元素添加到结果中
#
# li = [11,22,33,44,55]
# result = filter(lambda a:a > 33,li)
# print(list(result))

# li = [11,22,33,44,55]
# def f1(args):
# result = []
# for i in args:
# result.append(100+i)
#
# return result
# r = f1(li)
# print(list(r))


# map 将函数返回值添加到结果中
# li = [11,22,33,44,55]
# map(函数,可迭代的对象(可以for循环的东西))
# def f2(a):
# return a + 100
# result = map(f2,li)
# result = map(lambda a: a +200,li)
# print(list(result))
# result = map(lambda a:a + 200,li)
# print(list(result))


# len
# s = "李杰"
# print(len(s))
#
# s = "李杰"
# b =bytes(s,encoding='utf-8')
# print(len(b))

# 2的10次方
# r = pow(2,10)
# print(r)

# 反转
# li = [11,22,1,1]
# li.reverse()
# reversed(li)
# print(li)

# 四舍五入
# r = round(1.8)
# print(r)

# 切片
# s = "sssssssssss"
# print(s[0:2:2])

# 排序
# li = [11,22,3,1,2]
# li.sort()
# print(li)

# zip
# l1 = ["qq",11,22,33]
# l2 = ["aa",11,22,33]
# l3 = ["zz",11,22,33]
# r = zip(l1,l2,l3)
# # print(list(r))
# temp = list(r)[0]
# ret = ' '.join(temp)
# print(ret)
posted @ 2016-06-04 02:35  PY-Kony  阅读(190)  评论(0编辑  收藏  举报