5、字符串

# coding=utf-8

print('###### 字符串 ######')
'''
像姓名，一句话描述这样的的文本
    使用单引号、双引号、三个单引号或三个双引号引起来的一些字符
    name = 'Tom'
    desc = """my name is Tom."""
    
特殊字符
    \   转义符     
    \r  回车      
    \n  换行      
    \t  tab键    
    \f  换页      
'''
print('I\'m Tom.')
# \r回车是输出到同一行，会覆盖\r之前的输出
print('I\'m \r Tom.')
# \n回车是输出到下一行，不会覆盖\n之前的输出
print('I\'m \n Tom.')
print('I\'m \f Tom.')

• string.center()

name = "Alex Li"

name.capitalize()  # 首字母大写
name.casefold()   # 大写全部变小写,不怎么用
name.center(50,"-")  # 输出 '---------------------Alex Li----------------------'
name.count('lex') # 统计 lex出现次数
name.encode()  # 将字符串编码成bytes格式
name.endswith("Li")  # 判断字符串是否以 Li结尾
"Alex\tLi".expandtabs(10) # 输出'Alex      Li'， 将\t转换成多长的空格 
name.find('A')  # 查找A,找到返回其索引， 找不到返回-1 

name = "my name is yerban"
print(name.find("n"))
# 3
print(name[name.find("n"):7])
# find()可用于切片

# 从右边开始查找第一个匹配的下标
print(name.rfind("a"))
# 15

• string.format()

format :
    >>> msg = "my name is {}, and age is {}"
    >>> msg.format("alex",22)
    'my name is alex, and age is 22'
    >>> msg = "my name is {1}, and age is {0}"
    >>> msg.format("alex",22)
    'my name is 22, and age is alex'
    >>> msg = "my name is {name}, and age is {age}"
    >>> msg.format(age=22,name="ale")
    'my name is ale, and age is 22'
format_map
    >>> msg.format_map({'name':'alex','age':22})
    'my name is alex, and age is 22'
msg.index('a')  返回a所在字符串的索引

• string.isdigit()

'9aA'.isalnum() # 是否为阿拉伯数字和字母 True
'9'.isdigit() # 是否整数
name.isnumeric  
name.isprintable
name.isspace
name.istitle
name.isupper

b="ddefdsdff_哈哈" 
b.isidentifier() #检测一段字符串可否被当作标志符，即是否符合变量命名规则
True

• string.join()

 "|".join(['alex','jack','rain'])

print("|".join(['alex', 'jack', 'rain']))
# alex|jack|rain
print("+".join(['1', '2', '3']))
# 1+2+3

name = "my name is yerban"

print(name.ljust(50, "*"))
# my name is yerban*********************************

print(name.rjust(50, "*"))
# *********************************my name is yerban

print("HL".lower())
# hl

print("hl".upper())
# HL

print("\nhl")
# 本身会有换行
print("\nhl".lstrip())
# 去掉左边换行符
print("hl\n".rstrip())
# 去掉右边换行符
print("    hl\n".strip())
# 去掉两边换行符或空格

• string.maketrans()

maketrans
    >>> intab = "aeiou"  #这是具有实际字符的字符串。. 
    >>> outtab = "12345" #这是具有相应映射字符的字符串.
    >>> trantab = str.maketrans(intab, outtab) #把实际字符映射为对应字符。
    >>> 
    >>> str = "this is string example....wow!!!"
    >>> str.translate(trantab)
    'th3s 3s str3ng 2x1mpl2....w4w!!!'

# partition() 方法用来根据指定的分隔符将字符串进行分割。
# 如果字符串包含指定的分隔符，则返回一个3元的元组，第一个为分隔符左边的子串，第二个为分隔符本身，第三个为分隔符右边的子串。
msg = "my name is  {name}, and age is {age}"
msg.partition('is')  
# 输出 ('my name ', 'is', ' {name}, and age is {age}') 

• string.replace()

print("alex li, chinese name is lijie".replace("li", "hl", 1))  #替换
# alex hl, chinese name is lijie

• string.split()

name = "my name is yerban"
# 将空格进行切分称列表
print(name.split())
# ['my', 'name', 'is', 'yerban']

# 将"+"进行切分称列表
print("1+2+3".split("+"))
# ['1', '2', '3']

print(name.swapcase()) # 大小写互换
# MY NAME IS YERBAN

print(name.title())
# My Name Is Yerban

 >>> name.zfill(40)
# '00000my name is {name}, and age is {age}'  填充0