Python string

Note content: Python escape character

Date of Note: 2017-10-24

The basic content of the string has been introduced in the basic data type, so I won't repeat it here.

• Python escape characters
• Python string operators
• Python triple quotes
• Python's string built-in functions

Python escape characters

When you need to use special characters in a character, Python uses a backslash () to escape the character. The following table:

Among them, \n and \t are the most commonly used, followed by escape quotes and escape backslashes

Python string operators

In the following table, the value of the variable a is the string "Hello", and the value of the b variable is "Python":

a ="Hello"
b ="Python"print("a +b Output result:", a + b)print("a *2 Output result:", a *2) #Output the content of a twice,*n, output the previous string n times
print("a[1]Output result:", a[1]) #Take value from subscript
print("a[1:4]Output result:", a[1:4]) #Intercept string subscript 1-Characters within 4, excluding 4print('hello world'[-1])  #Negative numbers take values in reverse order, so-1 is the value of the last subscript
print('hello world'[0:])  #Start from 0 and take all the following values
print('hello world'[:5])  #Start from 0, intercept to subscript 5if("H"in a):print("H is in variable a")else:print("H is not in variable a")if("M" not in a):print("M is not in variable a")else:text-align: left;print("M is in variable a")print(r'\n')print(R'\n')
# Add an r in front of the print statement to indicate that this is a raw string, which will escape some special characters
print(r'c:\test\abc\123')
# Capitalization is also possible
print(R'c:\test\abc\123')

# You can also write when declaring the string
s=r'c:\test\abc\123'print(s)

operation result:

a + b output: HelloPython
a * 2 Output result: HelloHello
a[1] Output result: e
a[1:4] Output result: ell
H is in variable a
M is not in variable a
 \n
 \n

Among the more commonly used ones are +, *, [], [:] and member operators.

Python string formatting

Python supports the output of formatted strings. Although very complicated expressions may be used in this way, the most basic usage is to insert a value into a string with the string format character %s.
In Python, string formatting uses the same syntax as the printf function in C language. If only simple usage is used, it can be used as printf. Code example:

print("My name is%s this year%d years old!"%('Xiao Ming',10))

operation result:

My name is Xiao Ming and I am 10 years old!

String formatting is seldom used. It’s a tasteless thing. Just know if there is such a thing.

Python string formatting symbols:

Formatting operator auxiliary instructions:

Python triple quotation marks

Python triple quotation marks allow a string to span multiple lines. The string can contain line breaks, tabs and other special characters. Code examples:

para_str ="""This is an example of a multi-line string
Multi-line strings can use tabs
TAB( \t )。
Line breaks can also be used[ \n ]。
"""
print(para_str)

operation result:

This is an example of a multi-line string
Multi-line strings can use tabs
 TAB (    )。
You can also use line breaks [
  ]。

Python's string built-in functions

The commonly used built-in functions of Python strings are as follows:

Several commonly used function code examples:

s ="hello..."
upper ="HELLO..."print("Convert the first character of s to uppercase:", str.capitalize(s))print("Number of occurrences of'l' in s:", s.count("l"))print("Does it end with '...'end:", s.endswith("..."))print("Does it end with 'h’开头：", s.startswith("h"))print("The subscript of'o' in s is (if not found, it will return-1）：", s.find("o"))print("The subscript of'o' in s is (if not found, an exception will be thrown):", s.index("o"))print("Replace the'o' of s with'c':", s.replace("o","c"))print("The largest letter in s is:",max(s))print("The smallest letter in s is:",min(s))print("Convert upper to lowercase:", upper.lower())print("Convert s to uppercase:", s.upper())print("Titleize s:", s.title())

seq =("a","b","c","d","e")  #String sequence
print("Combine the characters in seq:","".join(seq))print("The length of seq is:",len(seq))  #String sequences can also be used
print("The length of s is:",len(s))

s2 ="a,b,c,d,e,f,g"print("Separate the strings in s2 by commas", s2.split(","))

s3 ="This is swapcase method test"print("Convert the uppercase of the string in s3 to lowercase and lowercase to uppercase:", s3.swapcase())

s4 ="    Test      "print("Remove the left and right spaces of s4:", s4.strip())

operation result:

Convert the first character of s to uppercase: Hello...
Number of occurrences of'l' in s: 2
Does s end with "...": True
Whether to start with'h' in s: True
The subscript of'o' in s is (if not found, it will return -1): 4
The subscript of'o' in s is (if not found, an exception will be thrown): 4
Replace the'o' of s with'c': hellc...
The largest letter in s is: o
The smallest letter in s is:.
Convert upper to lowercase: hello...
Convert s to uppercase: HELLO...
Title s: Hello...
Combine characters in seq: abcde
The length of seq is: 5
The length of s is: 8
Separate the strings in s2 by commas ['a','b','c','d','e','f','g']
Convert the uppercase of the string in s3 to lowercase and lowercase to uppercase: tHIS IS SWAPCASE METHOD TEST
Remove the left and right spaces of s4: Test