Basic python knowledge and basic python tutorials

Basic python knowledge and basic python tutorials

Python has been used many times. I know all the basic things. However, if I have used it, I have mastered all the details. Today, we will go over python from start to end. From the original basic knowledge of python.

Although python3.x has been around for a long time, the most popular python version is still python2.x due to the poor popularity. I have generally used python2.7. Therefore, the syntax involved in the next step is python2.7.

from __future__ import division

  
After the introduction, the division operation results must be decimal. If you want to keep only the entire number of digits. Yes.
      
1 // 2 # The result is 0.
  

  
Power Operation
  
2 ** 3 is faster than pow (2, 3. We recommend that you use the former.

  
Hexadecimal numbers start with 0x and Octal numbers start with 0. Review.

  
Note the differences between the math module and the cmath module.
      
math.sqrt(-1)cmath.sqrt(-1)
  

  
If you want to directly run the python program when running the script without explicitly calling python, add the following sentence:
      
#!/usr/bin/env python
    
 
  
This script can be automatically executed if it has the executable permission. For example
      
Chmod a + x hello. py # Add executable permissions to all users. a stands for all, all, and x stands for executable permissions.
    
Hello. py # Simply write this sentence to enable python without using python hello. py.
  

  
Let's briefly talk about the repr function. I 've been confused by such a simple function for a long time. Essentially, it creates a new string that stores the value of a python expression in the string. Using the repr function, you can easily guide the expression result type
        
print repr(“hello”)
      
Result 'hello'
  
What if I use the str that I often confuse?
      
print str("hello")
    
 
  
Result hello. Note: no single quotes are provided.
  
Another example
      
print repr(1000L)print str(1000L)
    
 
  
1000L
1000

  
Input is not particularly useful. It is best to use raw_input when needed.
  
Next let's talk about string processing. Three single quotes in a row can be used for long strings. When the character string has a backslash \, you must note the escape. If you do not want to escape the character string
      
print r'hello'
    
 
  
Add an r to solve this problem.

Okay, so many reviews at the beginning. These are all details about python.