Python self-study (i)

1. Python Benefits

Simple, elegant, clear

Powerful module third-party library

Easy to transplant

Facing diagonal

Can be extended

2. Disadvantages

Code cannot be encrypted

Slow execution speed

3. Variable definition

The first letter must be a case, or underscore, in the alphabet. Cannot start with a number.

1) Example of variable assignment

eg

>>> x=123

>>> y=x

>>> ID (x)

22582176

>>> ID (y)

22582176

>>> x=100

>>> ID (x)

22580736

>>> ID (y)

22582176

>>> tast-date = 1

File "<stdin>", line 1

Syntaxerror:can ' t assign to operator; You cannot define a variable with a non-casing underline

>>> tast_date = 1

2) Variable value type

Boolean type: True,false

eg

If true:print ' DDD '

Ddd

Integral type, long integer, float type:

eg

>>> type (a)

<type ' Long ' >

>>> A = 2**34

>>> type (a)

<type ' int ' >

>>> a=1.34

>>> type (a)

<type ' float ' >

>>> a=3

>>> type (a)

<type ' int ' >

>>> b=2.3

>>> type (b)

<type ' float ' >

String:

>>> name= ' Wang '

>>> type (name)

<type ' str ' >

sequence Type: list, array ...

>>> name_list=[' Wang ', ' Bai ', ' GUI '

>>> type (name_list)

<type ' list ' >

4. Arithmetic

A) "/" division, the default is only the whole, can be followed by a decimal point.

>>> 3/2

1

>>> 3.0/2

1.5

b) Take dividend

>>> 10//2

5

>>> 10//4

2

>>> 10//3

3

C) Subtraction method

+ = "C+=a equals C=c+a"

*= "C*=a equals C=c*a"

**= "C**=a equals C=c**a"

d) and Operation &:

10 and 15 and the operation

1010 1111È10

10 20

1010 10100è

>>> & 20

0

>>> & 15

10

e) or operation:

10 20

1010 10100È11110 30

>>> 10 | 20

30

5. Comments

Single-line Comment: #

Multiline Comment: Three chapter quotes "" "or three double quotes" "" "", and the other can be formatted output

Tip: No difference between single and double quotes

6. Understanding character encoding

three character levels:assic(Default one byte) Unicode(two bytes) UTF-8(variable byte, kanji three bytes)

Overview: One byte 8 bits 111111 256 words, two bytes 16 bits 65,536 characters

1024 bytes =1kb

1) (ACCIS)

An example of a byte:

>>> Ord (' a ')

97; A corresponds to a few bits of 8 bits

>>> Ord (' A ')

A corresponds to a certain number of 8 bits.

Corresponds to each of each of the corresponding 256-digit counterparts.

2) UTF-8 Code: Variable

Save in English with a byte, the Chinese character is stored in three bytes.

>>> a= ' Wang '

>>> type (a)

<type ' str ' >

>>> a=u ' Wang '

>>> type (a)

<type ' Unicode ' >

>>> A

U ' Wang '

>>> Name=u ' king brother '

>>> type (name)

<type ' Unicode ' >

>>> Name

U ' \u738b\u67cf\u8d35 '

>>> name = "Little Brother Wang"

>>> Name

' \xe7\x8e\x8b\xe6\x9f\x8f\xe8\xb4\xb5 '

>>> name = u "little brother Wang"

>>> Name

U ' \u738b\u67cf\u8d35 '

3) Convert Unicode to UTF-8

>>> name = U ' King little Brother '

>>> Name

U ' \u738b\u67cf\u8d35 '

>>> name.encode (' Utf-8 ')

' \xe7\x8e\x8b\xe6\x9f\x8f\xe8\xb4\xb5 '

4) UTF-8 converted to Unicode

>>> wang= "little brother Wang"

>>> Wang

' \xe7\x8e\x8b\xe6\x9f\x8f\xe8\xb4\xb5 '

>>> wang.decode (' Utf-8 ')

U ' \u738b\u67cf\u8d35 '

Tips:

Python system By default is the Assic code encoding format, corresponding to a byte, so in Python in Chinese, there will be problems, should be converted to UTF8 encoding format

#_ *_ Coding:utf-8 _*_

Name = u "Chinese"

Print Name

Tips:

In the system read into memory default is Unicode format, storage to the hard disk can be stored in UTF-8 format, because the Unicode default is two bytes of storage, occupy space.

8. Import Module

Three ways to import:

1) Import ModuleName

2) from module import Sayhi

3) Import ModuleName as NewName

eg

Import SYS

Print SYS.ARGV

Or

From sys import ARGV

Print argv

Or

from sys import *; not recommended

Or

Import Multiprocessing as Nulte

=========================

eg

A) invoking system commands

>>> Import OS

>>> os.system (' DF ')

Filesystem 1k-blocks used Available use% mounted on

/dev/sda3 18423556 1691736 15795936 10%/

Tmpfs 405824 0 405824 0%/dev/shm

/DEV/SDA1 198337 29668 158429 16%/boot

0 ; The default output returns the return value of the previous instruction

==> The return value to be stored and output

>>> Cru_dir = Os.system (' pwd ')

/root/python/day01

>>> Print Cru_dir

0

b) How to output the output?

Pour into import commands module

>>> Import Commands

>>> res = commands.getstatusoutput (' pwd ')

>>> Res

(0, '/root/python/day01 ')

3) Pour into the import sys module

[email protected] day01]# cat test1.py

Import Sys

Print SYS.ARGV

Print Sys.argv[2]

[[email protected] day01]# python test1.py a b C

[' test1.py ', ' A ', ' B ', ' C ']

B

9. User interaction

1) raw_input

[email protected] day01]# cat test2.py

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Name = raw_input(' Please input your name: ')

Age = Raw_input (' Age: ')

Print name, age

[email protected] day01]# cat test2.py

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Name = raw_input (' Please input your name: ')

Age = Raw_input (' Age: '); raw_input whatever input is interpreted as a string

Job = Raw_input (' job: '), can be converted to a number by int (raw_input (' Age: '), or directly with input (' Age: '), note: The imput is followed by the original ecology, what was before, is what, must indicate what is Type, etc., or there will be errors.

Salary = Raw_input (' Salary: ')

Print ""

Name:%s

Age:%s

Job:%s,%s for string,%d for number,%f for floating point

Salary:%s

-----------------

"% (name,age,job,salary)

imput Example:

[Email protected] day01]# vim test2.py

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Name = raw_input (' Please input your name: ')

Age = Input (' Age: ')

Job = Raw_input (' Job: ')

Salary = Raw_input (' Salary: ')

Print type (age)

Print ""

Name:%s

Age:%s

Job:%s

Salary:%s

-----------------

"% (name,age,job,salary)

[email protected] day01]# python test2.py

Please input your Name:wangbaigui

Age:28

Job:it

salary:2w

<type ' int ' >

Name:wangbaigui

Age:28

Job:it

salary:2w

-----------------

[Email protected] day01]# vim test2.py

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Age = 28

Name = raw_input (' Please input your name: ')

Age = Input (' Age: ')

Job = Raw_input (' Job: ')

Salary = Raw_input (' Salary: ')

Print type (age)

Print ""

Name:%s

Age:%s

Job:%s

Salary:%s

-----------------

"% (name,age,job,salary)

[email protected] day01]# python test2.py

Please input your Name:wangbaigui

Age:age

Job:it

salary:3w

<type ' int ' >

Name:wangbaigui

Age:28

Job:it

salary:3w

10. Process Control

1) If ... else ... Example:

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Name = raw_input (' Please input your name: ')

Age = Input (' Age: ')

Job = Raw_input (' Job: ')

Salary = Raw_input (' Salary: ')

If age > 30:

Meg = ' You're so old ... '

Elif Age >20:

Meg = ' ... '

Else

Meg = ' You're so yongest ... '

Print ""

Name:%s

Age:%d

Job:%s

Salary:%s

-----------------

%s

"% (Name,age,job,salary,meg)

2) for Loop

[email protected] day01]# cat test4.py

#!/usr/bin/env Ptyhon

#_ *_ Coding:utf-8 _*_

Name = raw_input (' Please input your name: ')

Job = Raw_input (' Job: ')

Salary = Raw_input (' Salary: ')

Relea_age = 28

For I in range (10):

Age = Input (' Age: ')

If Age >30:

Meg = "Think small ..."

elif age = = 28:

Meg = "Good!,you is right."

Break

Else

Meg = "Go to think"

Print Meg

Print "You had only%s times to Trye"% (9-i)

Print ""

Name:%s

Age:%d

Job:%s

Salary:%s

-----------------

%s

"% (Name,age,job,salary,meg)

3) While loop

[email protected] day01]# cat test5.py

Slect_num = input (' which num you want: ')

Count = 0

While Count < 100:

if Count = = Slect_num:

print ' You slect right:%s '% (slect_num)

Choice = Raw_input (' You want go on or contine (y/n) ')

if choice = = ' Y ':

While True:

Slect_num = input (' which num you want Agan: ')

If Slect_num <= count:

Print "Lookup alred past..,ples input newest num!"

Else

Break

Continue

Else

Break

Else

print ' Lookup ', count

Count +=1

Else

print ' alread more then 100. So bye! '

Python self-study (i)