字符的定义和操作

字符不具有修改的性质。

字符的定义：

# define
a = "Hello,world!"
b = 'Python is cool!'
c = str(range(4))
print(a)                               # Hello,world!
print(b)                               # Python is cool!
print(c)                               # range(0, 4)

字符的简单操作：

# 访问值
print(a [0])                                              # H
print(a [0:4])                                            # Hell
print(a [:4])                                             # Hell
print(a [4:-1])                                           # o,world
print(a [4:])            #可以取到最后一位                # o,world!

# 不可修改.
# 通过重新赋值的方式来“改变”一个已有的字符串。新的值，可以和新的差不多，也可能和原有的字符串完全不同。

# change
a = a [0:6] + "python"                                  # Hello,python
print(a)
a = 'this is a new world for me'
print(a)                                                 # this is a new world for me

字符的.XXXX操作：

# operation
print(a.count("is"))                                     # 2
print(a.capitalize())      # 首字母大写                  # This is a new world for me
print(b.casefold())                                      # python is cool!
print(a.center(50,"*"))                                  # ************this is a new world for me************

print(a.encode("utf-8"))  # 转码                                          # b'this is a new world for me'
print(a.endswith("hbb"))  # 判断是否以“ ”结束                            # False
print("hbb	bing".expandtabs(20))      #将	换成多少的空格                # hbb                 bing

print(a.find("a"))                                                       # 8
print(a.find("g"))                                                       # -1

# format:
introdution = """ -------info of {}---------
my name is {},
and age is {}"""
print(introdution.format("hbb","hbb",22))

introdution = """ -------info of {0}---------
my name is {0},
and age is {1}"""
print(introdution.format("hbb",22))

introdution = """ -------info of {name}---------
my name is {name},
and age is {age}"""
print(introdution.format(name = "hbb",age=22))
# a.format_map()

print(a.index("a"))                    # 8
d = "b8b"
e = "8bB"
print(d.isalnum())     # 是否为字符                 # True
print(d.isalpha())     # 是all字母
print(e.isdecimal())   # 是否是小数
print(e.isdigit())     # 是否都为数字
print(d.islower())     # 小写?
print(e.isupper())     # big write
print(d.isnumeric())
print(d.isspace())
print(d.isprintable())

print("|".join("h""b""b"))                       # h|b|b

intab =  "abcdef"
outtab = "123456"
new = a.maketrans(intab,outtab)                # 不懂什么鬼
print(new)


print(a.partition("e"))   # 以“”划分 （第一个）             # ('this is a n', 'e', 'w world for me')

print(a.swapcase())           # 大小写互换                    # THIS IS A NEW WORLD FOR ME
print(a.startswith("t"))

print(a.zfill(30))                                            #  0000this is a new world for me
print(a.center(30,"*"))                                      #   **this is a new world for me**
print(a.rjust(30,"*"))                                       # ****this is a new world for me
print(a.ljust(30,"*"))                                       # this is a new world for me****

东西很多，也很常用，不妨当工具来看。