python第一天

#一、字符串的魔法
# 1、num = 9 / 2
#    print(num)     //num=4.5

# 2、num = 9 // 2
#    print(num)     //num=4

# 3、name = "william"
#    if  "il" in name:
#       print("OK")
#    else:
#       print("Error")   //OK

# 4、v = 1 == 2
#    print(v)      //False


# 5、upper把小写字母转为大写
# num = "abcdefg"
# v = num.upper()
# print(v)         //ABCDEFG

#num = "LaiYing"
# v = num.upper()
# print(v)           //LAIYING

#6、bit_length 输出字符二进制长度
# a = 5
# len = a.bit_length()
# print(len)         //5D=101B a.bit.length=3

#7、字符串魔法
#str = "aLEx"
# s2 = "root"
# a = s1.title()        //title让每个单词首字母大写
# b = s1.upper()        //把每个小写字母转为大写
# c = str.lower()         //把大写字母转为小写
# print(a)                // ALEx
# print(b)                //ALEX
# print(c)                //alex

#8、统计字符串中字符出现次数
#test = "erererrtrtrttytyty"
#b = test.count("er")     //统计er在字符串test中出现的次数
# c = test.count('t',1,9)   //统计t在字符串的第1和第9个字符中出现的次数
# print(b)                 //  3
# print(c)

#练习：输入3次对应用户名及密码，错误三次就失败
# count = 0                   //输入3次对应用户名及密码，错误三次就失败
# while count < 3:
#     user = input('>>>')
#     passwd = input('<<<')
#     if user == 'WYC' and passwd == '123':
#         print("Welcome!")
#     count += 1

#9、设置填充字符或字符位置
# test = "asddfghjk"
# a = test.ljust(20,"*")       //设置宽度，并将内容居中
#                         # 20 代指总长度
#                         # *  空白未知填充，一个字符，可有可无
# b = test.rjust(20,"#")
# c = test.center(20,"$")
# print(a)
# print(b)
# print(c)
#
# asddfghjk***********
# ###########asddfghjk
# $$$$$asddfghjk$$$$$$

#10、查找字符的位置并输出
# 从开始往后找，找到第一个之后，获取其位置
# test = "qwertyuiop"
# a = test.find('r')
# print(a)   // 3

# 11、字符串中是否只包含 字母和数字
# test = "123"
# v = test.isalnum()
# print(v)
# str

# 12、是否是字母，汉字
# test = "as2df"
# v = test.isalpha()
# print(v)

# 13、当前输入是否是数字
# test = "二" # 1，②
# v1 = test.isdecimal()
# v2 = test.isdigit()
# v3 = test.isnumeric()
# print(v1,v2,v3)


# 14、是否存在不可显示的字符
# \t   制表符
# \n   换行
# test = "oiuas\tdfkj"
# v = test.isprintable()
# print(v)

# 15、判断是否全部是空格
# test = ""
# v = test.isspace()
# print(v)

#16、join将字符串中的每一个元素按照指定分隔符进行拼接
# a = "asdasdasdasd"
# b = "_"
# c = b.join(a)
# print(c)
#a_s_d_a_s_d_a_s_d_a_s_d

#17、判断是否全部是大小写 和 转换为大小写
# test = "Alex"
# v1 = test.islower()
# v2 = test.lower()
# print(v1, v2)

# v1 = test.isupper()
# v2 = test.upper()
# print(v1,v2)

#18、将指定字符串替换为指定字符串
# test = "ererererererer"
# a = test.replace("er","zx")
# b = test.replace("er","zx",1)
# c = test.replace("er","zx",4)    //替换test字符串中前4个er为zx
# print(a)
# print(b)
# print(c)
# zxzxzxzxzxzxzx
# zxerererererer
# zxzxzxzxererer

# 19、split分割为指定个数
# test = "qwertyuiop"
# a = test.split("w",2)
# b = test.rsplit("w",2)
# print(a)
# print(b)
# ['q', 'ertyuiop']
# ['q', 'ertyuiop']


# 20、swapcase大小写转换
# test = "aLeWcF"
# a = test.swapcase()
# print(a)
# AlEwCf

# 二、黑魔法
#1、for循环
# for 变量名 in 字符串:
#     变量名
# break
# continue

#2、len获取字符串长度
# index = 0
# while index < len(test):
#     v = test[index]
#     print(v)
#
#     index += 1
# print('=======')


# 3、切片：提取第2个字符和第5个字符之间的内容
# test = "qwertyasdfghjklpoi"
# a = test[2:5]
# print(a)               //ert


# test = "qweqweqwe"
# a = len(test)
# print(a)                //9

#4、获取连续或不连续的数字，
# # Python2中直接创建在内容中
# # python3中只有for循环时，才一个一个创建
# 帮助创建连续的数字,通过设置步长来指定不连续
# v = range(0, 100, 5)

# a = range(10)
# b = range(1,10)
# c = range(1,100,5)   // 帮助创建连续的数字,通过设置步长来指定不连续
# i=0
# print(a)
# while i< 10:
#     print(a[i])
#     i +=1
# 0
# 1
# 2
# 3
# 4
# 5
# 6
# 7
# 8
# 9