The third day of getting started with Python

Source: Internet
Author: User
Tags printable characters string format

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

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