Python basic notes and python notes

Python basic notes and python notes

1. Environment variable settings:

 

Edit the system variable Path and add two new paths.

C: \ Python26 can be used to call python.exe.

C: \ python26 \ Scripts calls third-party Scripts added to Python through extension.

 

2. If you use Chinese characters, the character set must be specified in the first line of the py file:

 

#-*-Coding: UTF-8 -*-

Or

# Encoding: UTF-8

 

3. Variable Length Parameter

 

 

4. Use global variables

 

You can use the global keyword before a variable name.

A = 5

Def fun (x ):

Global

Return x +

 

5. lambda expressions

 

Anonymous function, single-row small function

 

Format: labmda parameter: Expression

Returns the value of the expression.

 

It can contain a single parameter expression and cannot contain statements, but can call other functions.

Fun = lambda x: x * x-x

Fun (3)

 

Def show ():

Print 'lambda'

F = lambda: show ()

F ()

 

Def shown (n ):

Print 'lambda '* n

Fn = lambda x: shown (x)

Fn (2)

 

6. run scripts

 

Python code

1. # Encoding = UTF-8
3. Def show ():
4. Print u' I am a module .'
6. If _ name _ = '_ main __':
7. Show ()

 

7. Random Number

 

Import random

Random. random () # generate a random floating point number [)

Random. randint (a, B) # generate an integer between [a, B] (including a and B)

 

 

8. input parameters in the command line

 

 

Def prompt (prompt ):

Return raw_input (prompt). strip ()

Name = prompt ("Your Name :")

 

9. Python characters

In python, the character is a string of 1.

Obtain all characters of a string:

 

Python code

1. >>> String = 'abcxyz'
2. >>> Char_list = list (string)
3. >>> Print char_list
4. ['A', 'B', 'C', 'x', 'y', 'z']
5. >>> Char_list = [c for c in string]
6. >>> Print char_list
7. ['A', 'B', 'C', 'x', 'y', 'z']
8. >>># Obtain a set of all characters of a string
9. >>> Import sets
10. >>> Char_set = sets. Set ('abbcc ')
11. >>> Print char_set
12. Set (['A', 'C', 'B'])
13. >>> Print ','. join (char_set)
14. A, c, B
15. >>> Type (char_set)
16. <Class 'sets. set'>
17. >>> For c in char_set:
18. Print c
19. A
20. C
21. B

 

10. Conversion of characters and character values

Converts a character to an ascii code. The built-in function ord ():

 

>>> Ord ('A ')

97

 

Convert ascii code to character. built-in function chr ():

 

>>> Chr (97)

'A'

 

Convert unicode characters to unicode codes. The built-in function ord ():

 

>>> Ord (U' \ u2020 ')

8224

 

Converts a unicode code to a unicode character. The built-in function unichr ():

 

>>> Unichr (8224)

U' \ u2020'

 

11. test whether the object is a class string

Isinstance (anobj, basestring)

 

12. sys. argv

List of command line parameters passed to the Python script. Argv [0] is the script name.

 

Python code

1. # _ * _ Coding: UTF-8 _*_
2. Import sys
3. If _ name _ = "_ main __":
4. If len (sys. argv) <2:
5. Print "Need a argument! "
6. Sys. exit (1)
7. Arg = sys. argv [1]
8. Print 'you input a argument: ', arg