The string is the most commonly used data type in Python. We can use quotation marks (' or ') to create a string.
Creating a string is simple, as long as you assign a value to the variable.
Var1 = ' Hello world! ' var2 = "Python runoob"
Python accesses a value in a string
Python does not support single character types, and one character is also used as a string in Python.
Python to access substrings, you can use square brackets to intercept strings
1 ' Hello world! ' 2 " Python Runoob " 3 4 Print " ", Var1[0]5print"", var2 [1:5]
View CodePython string update
You can modify a string that already exists and assign it to another variable
1 ' Hello world! ' 2 3 Print " "'runoob! '
View CodePython escape character
Python uses a backslash (\) to escape characters when special characters are needed in characters
Escape Character |
Description |
\ (at end of line) |
Line continuation character |
\\ |
Backslash symbol |
\‘ |
Single quotation marks |
\" |
Double quotes |
\a |
Bell |
\b |
BACKSPACE (Backspace) |
\e |
Escape |
\000 |
Empty |
\ n |
Line break |
\v |
Portrait tab |
\ t |
Horizontal tab |
\ r |
Enter |
\f |
Page change |
\oyy |
Octal number, the character represented by YY, for example: \o12 for newline |
\xyy |
Hexadecimal number, the character represented by YY, for example: \x0a for line break |
\other |
Other characters are output in normal format |
Python string operator
operator |
Description |
Example |
+ |
String connection |
>>>a + b 'hellopython' |
* |
Repeating output string |
>>>a * 2 'hellohello' |
[] |
Getting characters in a string by index |
>>>a[1] 'e' |
[ : ] |
Intercept part of a string |
>>>a[1:4] 'ell' |
Inch |
Member operator-Returns TRUE if the string contains the given character |
>>>"H" in a True |
Not in |
Member operator-Returns TRUE if the string does not contain the given character |
>>>"M" not in a True |
R/r |
Raw string-Raw string: all strings are used directly as literal meanings, without escaping special or non-printable characters. The original string has almost exactly the same syntax as a normal string, except that the first quotation mark of the string is preceded by the letter "R" (which can be case). |
>>>print r \ n ' \n >>> print r'\ n ' \n |
% |
format string |
|
Python string formatting symbols:
symbols |
Description |
%c |
Formatting characters and their ASCII code |
%s |
formatting strings |
%d |
formatting integers |
%u |
Formatting an unsigned integer |
%o |
Formatting an unsigned octal number |
%x |
formatting unsigned hexadecimal numbers |
%x |
Format unsigned hexadecimal number (uppercase) |
%f |
Format floating-point numbers to specify the precision after a decimal point |
%e |
Format floating-point numbers with scientific notation |
%E |
function with%e, format floating-point numbers with scientific notation |
%g |
Shorthand for%f and%e |
%G |
Shorthand for%f and%E |
%p |
Format the address of a variable with hexadecimal number |
Formatting operator Auxiliary directives:
symbols |
function |
* |
Define width or decimal precision |
- |
Used for left justification |
+ |
Show plus sign (+) in front of positive number |
<sp> |
Show spaces in front of positive numbers |
# |
Displays 0 (' 0 ') before the octal number, preceded by ' 0x ' or ' 0X ' in hexadecimal (depending on ' x ' or ' x ') |
0 |
The displayed number is preceded by ' 0 ' instead of the default space |
% |
' percent ' output a single '% ' |
(VAR) |
mapping variables (dictionary parameters) |
M.N. |
M is the minimum total width displayed, and n is the number of digits after the decimal point (if available) |
Python2.6 begins with the addition of a function str.format () that formats the string, which enhances the functionality of string formatting.
Python three-quote (triple quotes)
Three quotation marks in Python can be used to copy complex strings:
Python three quotes allow a string to span multiple lines, and the string can contain line breaks, tabs, and other special characters.
The syntax for a triple quotation mark is a pair of consecutive single or double quotes (usually paired).
Three quotes allow programmers to escape from the mire of quotes and special strings, keeping a small piece of string in the form of what is known as WYSIWYG.
A typical use case is that when you need a piece of HTML or SQL, it's very tedious to use a string combination to escape a special string.
1errhtml =" "2 <HTML><HEAD><TITLE>3 Friends CGI demo</title>4 <BODY><H3>ERROR</H3>5 <B>%s</B><P>6 <form><input Type=button Value=back7 onclick= "Window.history.back ()" ></FORM>8 </BODY></HTML>9 " "TenCursor.execute (" " One CREATE TABLE Users ( A Login VARCHAR (8), - uid INTEGER, - Prid INTEGER) the " ")
View CodeUnicode string
Defining a Unicode string in Python is as simple as defining a normal string:
The lowercase "u" before the quotation mark indicates that a Unicode string is created here. If you want to add a special character, you can use Python's Unicode-escape encoding.
The replaced \u0020 ID indicates that a Unicode character with a encoded value of 0x0020 is inserted at the given location (whitespace)
1 u'hello\u0020world! ' 2 u'Hello world! '
View CodePython string built-in functions
Method |
Description |
String.capitalize () |
Capitalize the first character of a string |
String.center (width) |
Returns the center of the original string and fills the new string with a space of length width |
String.count (str, beg=0, End=len (String)) |
Returns the number of occurrences of STR in a string, if beg or end specifies that the number of STR occurrences in the specified range is returned |
String.decode (encoding= ' UTF-8 ', errors= ' strict ') |
Decodes a string in the encoded format specified by encoding, if an error defaults to a ValueError exception unless errors specifies ' ignore ' or ' replace ' |
String.encode (encoding= ' UTF-8 ', errors= ' strict ') |
Encodes a string in the encoding format specified by encoding, if an error defaults to a ValueError exception unless errors specifies ' ignore ' or ' replace ' |
String.endswith (obj, beg=0, End=len (String)) |
Checks whether the string ends with obj, or returns False if beg or end specifies whether to end with obj in the specified range, or True if it is. |
String.expandtabs (tabsize=8) |
Turns the tab symbol in string strings to a space, and the default number of spaces for the tab symbol is 8. |
String.find (str, beg=0, End=len (String)) |
Detects if STR is contained in a string, and if beg and end specify a range, the check is contained within the specified range, and returns 1 if the index value is returned. |
String.Format () |
formatting strings |
String.index (str, beg=0, End=len (String)) |
Just like the Find () method, only if STR does not report an exception in string. |
String.isalnum () |
If the string has at least one character and all characters are letters or numbers, return Return True, otherwise False |
String.isalpha () |
Returns True if the string has at least one character and all characters are letters. otherwise returns False |
String.isdecimal () |
Returns True if the string contains only a decimal number, otherwise False. |
String.isdigit () |
Returns True if the string contains only a number, otherwise False. |
String.islower () |
Returns True if the string contains at least one case-sensitive character, and all of these (case-sensitive) characters are lowercase, otherwise False |
String.isnumeric () |
Returns True if the string contains only numeric characters, otherwise False |
String.isspace () |
Returns True if the string contains only spaces, otherwise False is returned. |
String.istitle () |
Returns True if string is heading (see Title ()), otherwise False |
String.isupper () |
Returns True if the string contains at least one case-sensitive character, and all of these (case-sensitive) characters are uppercase, otherwise False |
String.Join (seq) |
Merges all the elements in the SEQ (the string representation) into a new string, using string as a delimiter |
String.ljust (width) |
Returns the left alignment of an original string and fills the new string with the width of length with a space |
String.Lower () |
Converts all uppercase characters in a string to lowercase. |
String.lstrip () |
Truncate the left space of a string |
String.maketrans (Intab, Outtab]) |
The Maketrans () method is used to create a conversion table of character mappings, for the simplest invocation of two parameters, the first argument is a string that represents the character that needs to be converted, and the second argument is the target of the string representation of the transformation. |
Max (str) |
Returns the largest letter in the string str . |
Min (str) |
Returns the smallest letter in the string str . |
String.partition (str) |
A bit like the combination of find () and split (), from the first position where Str appears, divide the string into a 3-element tuple (STRING_PRE_STR,STR,STRING_POST_STR), if string STR is not included in the STRING_PRE_STR = = string. |
String.Replace (str1, str2, Num=string.count (STR1)) |
Replace the str1 in string with the str2, if NUM is specified, the replacement is no more than num times. |
String.rfind (str, Beg=0,end=len (String)) |
Similar to the Find () function, it is just looking from the right. |
String.rindex (str, Beg=0,end=len (String)) |
Similar to index (), but starting from the right. |
String.rjust (width) |
Returns the right alignment of the original string and fills the new string with the width of the length with a space |
String.rpartition (str) |
Similar to the partition () function, it is just looking from the right. |
String.rstrip () |
Removes a space at the end of a string string. |
String.Split (str= "", Num=string.count (str)) |
Slice string with a delimiter of STR, if NUM has a specified value, only the NUM substring is delimited |
String.splitlines ([keepends]) |
Separated by rows (' \ r ', ' \ r \ n ', \ n '), returns a list containing the rows as elements, if the argument keepends is False, does not contain a newline character, and if true, the newline character is preserved. |
String.startswith (obj, Beg=0,end=len (string)) |
Checks whether the string starts with obj, returns True, or False. If beg and end specify a value, the check is within the specified range. |
String.strip ([obj]) |
Execute Lstrip () and Rstrip () on string |
String.swapcase () |
Flip the case in a string |
String.title () |
A string that returns "header", meaning that all words start with uppercase and the remaining letters are lowercase (see istitle ()) |
String.translate (str, del= "") |
Converts a string of characters according to the table given by STR, which contains 256 characters, The characters to filter out are placed in the Del parameter |
String.upper () |
Convert lowercase letters in string to uppercase |
String.zfill (width) |
Returns a string of length width, the original string is right-aligned, and the front padding is 0 |
String.isdecimal () |
The Isdecimal () method checks whether a string contains only decimal characters. This method exists only in Unicode objects. |
6 Python Data Type-string