Python string manipulation

1, go to the space and special symbols

S.strip () S.lstrip () S.rstrip () S.strip (). Lstrip (). Rstrip ()

declaration : S is a string, RM is a sequence of characters to be deleted

S.strip (RM) Remove the characters from the beginning and end of the s string in the RM delete sequence

S.lstrip (RM) Delete the character in the S string at the beginning of the RM delete sequence

S.rstrip (RM) Removes the character from the end of the S string that is located in the RM delete sequence

2. Copying strings

#strcpy (str1,str2) str1 = ' strcpy ' str2 = str1str1 = ' strcpy2 ' Print str2

3. Connection string

#strcat (str1,str2) str1 = ' strcat ' str2 = ' append ' str1 + = Str2print str1

4. Find characters

#strchr (STR1,STR2) # < 0 for not found str1 = ' strchr ' str2 = ' s ' nPos = Str1.index (str2) Print NPos

5. Comparing strings

#strcmp (str1,str2) str1 = ' strchr ' str2 = ' strch ' Print cmp (STR1,STR2)

6. Whether the scanned string contains the specified characters

#strspn (str1,str2) str1 = ' 12345678 ' str2 = ' 456 ' #str1 and chars both in str1 and Str2print Len (STR1 and STR2)

7. String length

#strlen (str1) str1 = ' strlen ' Print len (str1)

8. Converting uppercase and lowercase characters in strings

S.lower () #小写 s.upper () #大写 s.swapcase () #大小写互换 s.capitalize () #首字母大写 string.capwords (S) #这是模块中的方法. It separates S with the split () function, then uses capitalize () to capitalize the first letter, and then merges it with join () #实例: #strlwr (sStr1) str1 = ' jcstrlwr ' str1 = Str1.upper () #str1 = Str1.lower () Print str1

9. Append a string of the specified length

#strncat (str1,str2,n) str1 = ' 12345 ' str2 = ' abcdef ' n = 3str1 + = Str2[0:n]print str1

10. String specified length comparison

#strncmp (str1,str2,n) str1 = ' 12345 ' str2 = ' 123BC ' n = 3print cmp (str1[0:n],str2[0:n])

11. Copy characters of the specified length

#strncpy (str1,str2,n) str1 = ' str2 = ' 12345 ' n = 3str1 = Str2[0:n]print str1

12. Replace the first n characters of a string with the specified characters

str1 = ' 12345 ' ch = ' r ' n = 3STR1 = n * ch + str1[3:]print str1

13. Scan string

#strpbrk (str1,str2) str1 = ' Cekjgdklab ' str2 = ' gka ' NPos = -1for C in str1:    if C in str2:        NPos = Str1.index (c)        b Reakprint NPos

14. Flip String

#strrev (str1) str1 = ' ABCDEFG ' str1 = Str1[::-1]print str1

15. Find string

#strstr (str1,str2) str1 = ' ABCDEFG ' str2 = ' cde ' Print str1.find (str2)

16. Split string

#strtok (str1,str2) str1 = ' Ab,cde,fgh,ijk ' str2 = ', ' str1 = Str1[str1.find (str2) + 1:]print str1# or s = ' Ab,cde,fgh,ijk ' Prin T (S.split (', '))

17. Connection string

delimiter = ', ' mylist = [' Brazil ', ' Russia ', ' India ', ' China ']print delimiter.join (mylist)

18, the implementation of addslashes in PHP

def addslashes (s):    d = {' ' ': ' \ \ ' ', ' ' ': ' \ \ ', '/': ' \\\0 ', ' \ \ ': ' \\\\ '}    return '. Join (D.get (c, c) for C in s) s = "John ' Johny ' Doe (a.k.a. \" Super joe\ ") \\\0" Print sprint addslashes (s)

19. Display only letters and numbers

def onlycharnum (s,oth= "):    s2 = S.lower ();    Fomart = ' abcdefghijklmnopqrstuvwxyz0123456789 ' for    C in S2:        if not C in Fomart:            s = s.replace (c, ');    Return S;print (Onlystr ("a000 aa-b"))

20. Intercepting strings

str = ' 0123456789 ' str[0:3]     str[:]       str[6:]      str[:-3]     str[2]       str[-1]      str[::-1]    str[-3:- 1]   str[-3:]     str[:-5:-3]

21. String alignment at output

S.ljust (Width,[fillchar]) #输出width个字符, s left-aligned, the insufficient portion is filled with Fillchar, the default is a space. S.rjust (Width,[fillchar]) #右对齐 s.center (width, [Fillchar]) #中间对齐 s.zfill (width) #把S变成width长, and right-aligned, with less than 0 complement

22. Search and Replace in string

S.find (substr, [Start, [end]]) #返回S中出现substr的第一个字母的标号, returns 1 if there is no substr in S. The start and end functions are equivalent to searching for S.index (substr, [Start, [end]) #与find () in S[start:end], except that when there is no substr in S, a run-time error is returned S.rfind (substr , [Start, [end]]) #返回S中最后出现的substr的第一个字母的标号, if S does not have substr then return-1, that is, the first occurrence of the substr from the right of the first letter marking S.rindex (substr, [Start, [end]]) S.count (substr, [Start, [end]]) #计算substr在S中出现的次数 s.replace (Oldstr, Newstr, [Count]) #把S中的oldstar替换为newstr, Count is the number of replacements. This is a common form of substitution, and there are some functions to replace s.strip ([chars]) with special characters #把S中前后chars中有的字符全部去掉, which can be understood as replacing S before and after chars to none S.lstrip ([chars]) S.rstrip ([ Chars]) S.expandtabs ([tabsize]) #把S中的tab字符替换没空格, each tab is replaced by a tabsize space, which defaults to 8

23. Segmentation and combination of strings

S.split ([Sep, [Maxsplit]]) #以sep为分隔符, divide s into a list. Maxsplit represents the number of splits. The default delimiter is a white-space character s.rsplit ([Sep, [Maxsplit]]) s.splitlines ([keepends]) #把S按照行分割符分为一个list, and Keepends is a bool value, Row separators are preserved if they are true for each row. S.join (seq) #把seq代表的序列-string sequence, connected by s

24, the mapping of the string, this function contains two functions

The String.maketrans (from, to) #返回一个256个字符组成的翻译表, where the characters from the from are converted to by one by one, so the from and to must be equal in length. S.translate (Table[,deletechars]) # Use the above function for the post-natal translation table, translate s for translation, and delete the characters in the Deletechars. It is important to note that if S is a Unicode string, then the Deletechars parameter is not supported, and the same functionality can be achieved by translating a character to none. You can also use the functionality of the codecs module to create more powerful translation tables.

25, string and a pair of encoding and decoding functions

S.encode ([encoding,[errors]]) # Where encoding can have a variety of values, such as gb2312 GBK gb18030 bz2 zlib Big5 bzse64, etc. are supported. The default value for errors is "strict", which means unicodeerror. Possible values are ' ignore ', ' replace ', ' xmlcharrefreplace ', ' backslashreplace ' and all the values registered by Codecs.register_error. This section covers the codecs module, not the S.decode ([encoding,[errors])

26, the string test, the judgment function, this kind of function is not in the string module, these functions return is the BOOL value

S.startswith (Prefix[,start[,end]]) #是否以prefix开头 S.endswith (Suffix[,start[,end]) #以suffix结尾 s.isalnum () #是否全是字母和数字, and has at least one character S.isalpha () #是否全是字母, and has at least one character s.isdigit () #是否全是数字, and has at least one character s.isspace () #是否全是空白字符, and has at least one character s.islower () # Whether the letters in S are all lowercase s.isupper () #S中的字母是否便是大写 s.istitle () #S是否是首字母大写的

27, the String type conversion function, these functions only in the string module has

String.atoi (S[,base]) #base默认为10, if 0, then s can be 012 or 0x23 This form of string, if it is 16 then s can only be 0x23 or 0x12 this form of String String.atol (S[,base] ) #转成long String.atof (S[,base]) #转成float

Once again, the string object is immutable, meaning that you cannot change a part of the character after Python creates a string. Any of the above functions will return a new string after the string has been changed, and the original is not changed. In fact, this is also a workaround, you can use S=list (s) This function to change S into a single character as a member of the list, so you can use the s[3]= ' a ' method of changing the value, and then use s= "". Join (s) revert to a string