The third day of getting started with Python

Python string operator

The following table instance variable a value is the string "Hello" and the B variable value is "Python":

operator	Description	Example
+	String connection	A + B output result: Hellopython
*	Repeating output string	A*2 Output Result: Hellohello
[]	Getting characters in a string by index	A[1] Output result e
[ : ]	Intercept part of a string	A[1:4] Output results ell
Inch	Member operator-Returns TRUE if the string contains the given character	' H ' in a output result 1
Not in	Member operator-Returns TRUE if the string does not contain the given character	' M ' not in a output result 1
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 ')print( r' \ n ')

Python string formatting

Python supports the output of formatted strings. Although this may use a very complex expression, the most basic usage is to insert a value into a string that has the string format of%s.

In Python, string formatting uses the same syntax as the sprintf function in C

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 Triple Quote

Python three quotes allow a string to span multiple lines, and the string can contain line breaks, tabs, and other special characters. Examples are as follows

1 # !/usr/bin/python3 2  3 """ This is an instance of a multiline string 4 multi-line strings can use tabs 5 TAB (\ t).  6 You can also use line break [\ n].  7"" "8print (PARA_STR)

The result is:

This is an instance of a multiline string multi-line string can be used with Tab tab (    ). You can also use the line break [  ].

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, a special string escape is cumbersome when you use a string combination.

" " cursor.execute (  'CREATE TABLE users (  login VARCHAR (8), UID Integer,prid INTEGER)')

The third day of getting started with Python