String

str
Text information
Single double quotation marks, three quotes
three characteristics quoted that can store more than one line, and keep the format

a= '''
i 
asd
asd

'''

print(a)

i 
asd
asd

Escape character

Escaped with a backslash
the windows \ n newline; Linux in \ r \ n: line feed

a='wo'
b='ai'
print(a+b)

woai

a= "let's go"
b= 'let\' go'
print(a,b)
# print(a,\nb)  错误

  File "<ipython-input-12-ec162cdbe208>", line 4
    print(a\n,b)
                ^
SyntaxError: unexpected character after line continuation character

Want to show \, you need to use \ \ backslash backslash transfer

a = 'abc\ndef\nghijk'
print(a)

abc
def
ghijk

Common escape character
\ line continuation, representation format is too long, can be used to write the next line,

# 续行
for b in\
range(1,10):
    print(b,end=' ')

1 2 3 4 5 6 7 8 9

format

String printed or filled in a format
fixed, the place is filled with Variational
Fill mode
- Traditional format, occupy a position with a placeholder%
  but predetermined format
  % s: string representing the placeholder
  % f: indicates floating placeholder
  % .2f represents two decimal places

Similarly decimal places in python

比如format中，“aaa  {:.2f}  asd”
在里面加上冒号，表示对里面的要求，然后加上 数字+f
 - format  没有规定必须是什么格式
     但是：字符串需要加上引号
 - format时使用{}来占位的，那如果想表示{}

s = "format是使用{}来占位的"
print(s)

format是使用{}来占位的

a = “I love %s”
print(a)
print(a%“XXX”)

I love %s
I love XXX

b = 'XXX'
a = "I love %s"    #单引号和双引号的字符串可以公用
print(a%b)#把这个式子展开就变为↓
print("I love %s"%'XXX')
# 和format有点像

print("I love {}".format(100))
# 将上面的写为多行
a = "I love {}"
b = input()
print(a.format(b))

I love XXX
I love XXX
I love 100
XSA
I love XSA

a = "{} {} !"
b = input()
c = input()
a = a.format(b,c)
print(a)
# print("{} {} !".format(b,c))

a
s
a s !

s = "{2}{1}{0}"
print(s.format("a","b","c"))#format里面的需要时字符串，字符串需要加上引号

cba

Named parameters

s = "a is {aa} , b is {bb} , c is {cc}"
print(s.format(aa="a",bb="b",cc="c"))

a is a , b is b , c is c

dictionary

Need prefixed with **, unpack the dictionary
Dictionary format { "": "", "": ""}

a_dict= {"a":"aa","b":"bb","c":"cc"}
s = "a is {a},b is {b},c is {c}"
print(a_dict)
print(s.format(**a_dict))

{'a': 'aa', 'b': 'bb', 'c': 'cc'}
a is aa,b is bb,c is cc

built-in function str

Python represented by the string str
- There are many built-in functions

Find class find, index

find Usage: is the result returned is the position of characters to find the first occurrence, regardless of the latter, -1 is returned if no
- Also start from the desired range to find
- rfind and lfind, start looking for the right, from the left to find
index and find similar, except that the index can not find out the character will complain, throw an exception

Analyzing class islower, isalpha

- isalpha，判断字符串是否是字母，不能区分中英文
- 判断是否全部是字母
- 空格和逗号都不是
- S.isalpha()  ，并返回结果（bool）

- islower  判断是否全是小写的
- 可以help（str。islower）
- 空格不影响
- 汉字不是小写
    - 汉字也不是大写
    - “阿瑟东”。isuper（）

Content judge

startswith/endswith
Check whether the beginning or end of the string to XXX
”asdasdzxcqwe“。startswith（”asd”）
Return result (bool)
Similarly you can know, start, end
“asdqweasd”。start（“qwe”）

Operating class

- format

- strip：删除字符串两边的空格或者字符，如果在后面逗号加上字符串，那么就会删掉想要的字符串
- 不返回值
- 只会从两边开始删除，并且山字符串空格不会删掉 
- rstrip，lstrip，删掉右边的，删掉左边的

- join：将两个字符串进行拼接,主要是以逗号为唤起点
- print（“a”。join（“as，阿瑟东，请问，q”））
    - 结果是“a”将后面的字符串中，逗号左右都加上一个“a”
    - 如果是对列表进行，则是将列表中的逗号进行替换

s = "asdasdasdqasdasdqwe"
s1 = "q"
# s.find(s1)

# s.find(s1,10) #表示从10的位置开始查找
s.rfind(s1)  # 从右边开始查找，查处的结果是正序的位置

# strip
a = "asdhho  qweoi kjh "

print(a)#看不出来
print(a.strip())
print(a,end='---')
print()
print(a.strip(),end="---")
print()
print(a.strip("asd"),end="---")

asdhho  qweoi kjh 
asdhho  qweoi kjh
asdhho  qweoi kjh ---
asdhho  qweoi kjh---
hho  qweoi kjh ---

print("a".join("a,d,f,q,q"))
print("a".join(["a","d","f","q","q"]))

aa,ada,afa,aqa,aq
aadafaqaq

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Private letter concerns

str module