Abstract: This paper introduces some basic operations in python string.
1, the slicing operation
Slicing operation is called with a selected portion of an element composed of regular operation of the new string in the given string .
Using str [Parameter 1: Parameter 2: Parameter 3] in the form of operations:
- Parameter 1: start position of the subscript, defaults to the first position
- Parameter 2: end position, need to specify, no default parameter contains two elements subscripted
- 3 parameters: the step size, default is 1, will be applied to the first parameter corresponding operation completion
- Three parameters can be negative, negative first two parameters is an indication position calculation starts from the last element: -1, -2, -3 ......
- Parameter 2 is the logarithm direction, this direction should match the parameters and 3, it would not output a corresponding sequence
. 1 password = ' 0123456789 ' 2 . 3 Print (password [0:. 5:. 1]) # 01234 ------ basic operation . 4 Print (password [. 1:. 5: 2]) # 13 is ------- - step operation . 5 . 6 Print (password [:. 5:]) # 01234 ------ default operation . 7 . 8 Print (password [-1: -11: -1]) # 9876543210 ------ - reverse operation . 9 Print (password [:: -. 1]) # 9876543210 -------- default reverse operation 10 . 11 Print (password [-2: -9: -2]) # 8642 ---- ----- steps in reverse order 12 Print(password [-9: -2:. 1]) # 1234567 ------ n sequential operation 13 is 14 Print (password [0:. 8: -2]) # no output 15 Print (password [-2: -9 : 1]) # no output
2, the search operation
Find operation commonly used in python there: find, index, count, rfind, rindex
find ( 'target sub-string', position 1, position 2)
- Return Value: Returns the position if found, or -1 if not found
- The next two parameters is omitted, to find the target in the entire string substring
index：
- And find the same, with one difference: not find the substring, then an error
count：
- Return Value: the number of the sought substring
rfind：
- And find the same, just start looking from the right
rindex：
- And the same index, just start looking from the right
1 str='hello python nice to meet you' 2 3 print(str.find('nice')) #13 4 print(str.find('nice',10,17)) #13 5 print(str.find('hi')) #-1 6 7 print(str.index('nice')) #13 8 print(str.index('nice',10,17)) #13 9 # print(str.index('hi')) # erroy 10 11 print(str.count('nice')) #1 12 print(str.count('nice',10,17)) #1 13 print(str.count('hi')) #0 14 15 print(str.rfind('nice')) #13 16 print(str.rfind('nice',10,17)) #13 17 print(str.rfind('hi')) #-1 18 19 print(str.rindex('nice')) #13 20 print(str.rindex('nice',10,17)) #13 21 #print(str.rindex('hi')) # erroy
3, modify operation
Modifying operation in python has commonly used: replace, split, join three important ways. Another case conversion, delete blank cells, such as its non-critical method
Replace ( 'substring old', 'new substring', replacing the number)
- Returns: a new string
- New for a long time
Split ( 'split flag substring', to find the number of times)
- Returns: List
- After generating a list of spaced apart, and the marker delete substring
Split string. Join (list)
- Returns: String
- The list elements in order to connect with a string divided
1 str='hello python nice to meet you' 2 3 newstr=str.replace('to','kkk',1) 4 print(str) # hello python nice to meet you 5 print(newstr) # hello python nice kkk meet you 6 7 list=str.split('to') 8 print(list) #['hello python nice ', ' meet you'] 9 10 List=['aa', ' BB ' , ' CC ' , ' dd ' ] . 11 newstr = ' and ' .join (List) 12 is Print (newstr) # AA and BB and CC and dd 13 is 14 myStr = " Hello World and the Python and itcast and itheima " 15 16 # . 1, capitalize () string initials . 17 new_str = mystr.capitalize () 18 is Print (new_str) . 19 # 2.title (): string of each word capitalized 20 is new_str =mystr.title () 21 is Print (new_str) 22 is # 3. Upper (): turn lowercase uppercase 23 is new_str = mystr.upper () 24 Print (new_str) 25 # 4. Lower (): turn uppercase to lowercase 26 is new_str = myStr. Lower () 27 Print (new_str) 28 29 # 1. the lstrip (): delete the left margin character 30 new_str = mystr.lstrip () 31 is Print (new_str) 32 # 2. The rstrip (): delete the right margin character 33 is new_str = mystr.rstrip () 34 is Print (new_str) 35 # 3.strip()：删除两侧空白字符 36 new_str = mystr.strip() 37 print(new_str) 38 39 ''' 输出 40 hello world and itcast and itheima and python 41 Hello World And Itcast And Itheima And Python 42 HELLO WORLD AND ITCAST AND ITHEIMA AND PYTHON 43 hello world and itcast and itheima and python 44 hello world and itcast and itheima and Python 45 hello world and itcast and itheima and Python 46 hello world and itcast and itheima and Python 47 48 '''
Its operation:
1 >>> mystr='hello' 2 >>> mystr.ljust(10) 3 'hello ' 4 >>> mystr.rjust(10) 5 ' hello' 6 >>> mystr.ljust(10,'.') 7 'hello.....' 8 >>> mystr.rjust(10,'.') 9 '.....hello' 10 >>> mystr.center(10) 11 ' hello '
4, the operation is determined
The determination operation in python are commonly used letter determination, determining numbers, alphanumeric combinations judgment, judgment spaces.
. 1 myStr = " Hello World and itcast and itheima and the Python " 2 . 3 # 1. startsWith (): determines whether the string beginning with a substring . 4 Print (mystr.startswith ( ' Hello ' )) # T . 5 Print (myStr. startsWith ( ' HEL ' )) # T . 6 Print (mystr.startswith ( ' HELS ' )) # F. . 7 . 8 . 9 # 2. endsWith (): determines whether the string that ends with a substring 10 Print (mystr.endswith ( 'Python ' )) # T . 11 Print (mystr.endswith ( ' Pythons The ' )) # F. 12 is 13 is 14 # 3. the isalpha (): letters 15 Print (mystr.isalpha ()) # F. 16 . 17 # 4. isdigit () : digital 18 is Print (mystr.isdigit ()) # F. . 19 MyStr1 = ' 12345 ' 20 is Print (mystr1.isdigit ()) # T 21 is 22 is # 5. The isalnum (): numbers or letters or a combination of 23 print(mystr1.isalnum()) #T 24 print(mystr.isalnum()) #F 25 mystr2 = 'abc123' 26 print(mystr2.isalnum()) #T 27 28 29 # 6.isspace(): 空白 30 print(mystr.isspace()) #F 31 mystr3 = ' ' 32 print(mystr3.isspace()) #T