Python3 Strings

Strings are the most commonly used data type in Python. We can use quotes ('or") to create strings.

Creating a string is simple, just assign a value to a variable. For example:

Python Accessing Values in Strings

Python does not support a single-character type; a single character is also used as a string in Python.

Python accesses substrings using square brackets[]to intercept strings. The syntax for string slicing is as follows:

variable[start index:end index]

Index values start with0as the starting value,-1is the starting position from the end.

As in the example below:

The execution result of the above example is:

var1[0]:  H
var2[1:5]:  unoo

Python String Update

You can intercept a part of a string and concatenate it with other fields, as in the example below:

The execution result of the above example is:

已更新字符串 :  Hello Example!

Python Escape Characters

When special characters are needed in characters, Python uses backslash\escape characters. As in the table below:

>>> print("line1 \
... line2 \
... line3")
line1 line2 line3
>>> 

>>> print("\\")
\

>>> print('\'')
'

>>> print("\"")
"

>>> print("\a")

>>> print("Hello \b World!")
Hello World!

>>> print("\000")

>>> 

>>> print("\n")


>>>

>>> print("Hello \v World!")
Hello 
       World!
>>>

>>> print("Hello \t World!")
Hello      World!
>>>

>>> print("Hello\rWorld!")
World!
>>> print('google example taobao\r123456')
123456 example taobao

>>> print("Hello \f World!")
Hello 
       World!
>>> 

>>> print("\110\145\154\154\157\40\127\157\162\154\144\41")
Hello World!

>>> print("\x48\x65\x6c\x6c\x6f\x20\x57\x6f\x72\x6c\x64\x21")
Hello World!

Use\r to implement percentage progress:

In the following example, we used different escape characters to demonstrate the effects of single quotes, newline, tab, backspace, form feed, ASCII, binary, octal and hexadecimal numbers:

Python String Operators

In the table below, the variable a in examples has the string value "Hello", and variable b has the value "Python":

print( r'\n' )
print( R'\n' )

The output result of the above example is:

a + b 输出结果： HelloPython
a * 2 输出结果： HelloHello
a[1] 输出结果： e
a[1:4] 输出结果： ell
H 在变量 a 中
M 不在变量 a 中
\n
\n

Python String Formatting

Python supports formatted string output. Although this may involve very complex expressions, the most basic usage is inserting a value into a string with the string format specifier %s.

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

The output result of the above example is:

我叫 小明 今年 10 岁!

Python string formatting symbols:

Formatting operator auxiliary directives:

Starting from Python 2.6, a new function for formatting strings was addedstr.format(), which enhances the functionality of string formatting.

Python Triple Quotes

Python triple quotes allow a string to span multiple lines; the string can contain newlines, tabs, and other special characters. An example is as follows:

The output of the above example is:

这是一个多行字符串的实例
多行字符串可以使用制表符
TAB (    )。
也可以使用换行符 [ 
 ]。

Triple quotes free programmers from the quagmire of quotes and special strings, keeping a small block of string in a so-called WYSIWYG (What You See Is What You Get) format from start to finish.

A typical use case is when you need a block of HTML or SQL. At this point, using string concatenation and special string escaping would be very cumbersome.

f-string

f-string was added in Python 3.6 and later versions. It is called a literal formatted string and is a new syntax for formatting strings.

Previously, we were used to using the percent sign (%):

f-stringThe formatted string starts withffollowed by the string. Expressions in the string are wrapped in curly braces {}. It will replace them with the computed value of the variable or expression. Example:

Using this method is clearly simpler; you no longer need to decide whether to use %s or %d.

In Python 3.8 and later, you can use=the symbol to concatenate the operation expression and its result:

Unicode Strings

In Python 2, ordinary strings are stored as 8-bit ASCII codes, while Unicode strings are stored as 16-bit Unicode strings, which can represent more character sets. The syntax used is to add a prefix before the stringu。

In Python 3, all strings are Unicode strings.

Python Built-in String Functions

Python's commonly used built-in string methods are as follows: