1, the interactive mode command
Start - " cmd -> cd c: \ -> dir
cd = change directory
dir = view a list of files in the current directory
cd .. Return to the previous directory
cd ../ .. Return to the parent directory
cd ../../ .. return to the upper level directory
cd ../../../ .. Return to the upper level directory
If we want to switch directories letter, correct usage is cd increased and an intermediate path "/ D" , such as cd / dd:
2 , #C: \ hello.txt .txt extension on behalf of file (extension), used to distinguish file types
.txt Notepad text file
.doc word file
.xls excel file
.ppt PPT file
.exe executable file
.jpg .png .jpeg pictures
.gif dynamic picture
.pdf PDF file
.mp4 .avi video
.py python file
.java java file
.c .h c source code
.php php file
.js javascript
3 , set the environment variable
Python added thereto path D: \ python \ Scripts \; D: \ python \;
4 , execution py program way :
1. Interactors, shortcomings can not be permanently stored procedures, primarily related to simple grammar test
2. file execution
5 , the Hello world program
print("hello world!")
variable
Variable to store the program operation process some of the results, in order to facilitate later recall
Naming variables
1. To descriptive
2. Variable names can only _, numbers, letters, spaces or special characters are not (#? <. , ¥ $ *! ~)
studentNumberPhthon ( hump body )
3. can not Chinese as a variable name
4. does not begin with a number
5. reserved characters can not be used
Constant : the same amount of pie = 3.141592653 ....
In py which all variables are variable , so use all uppercase variable names to represent this variable is constant
6, character encoding
The first table support Chinese called GB2312
1980 gb2312 6700+
1995 gbk1.0 20000
2000 gb18030 27000
big5 Taiwan
unicode Unicode encoding supported in all countries and regions
16 ** 2 = 65535 = deposit a uniform character occupies 2 bytes
UTF-8 = unicode extended set of variable length coded character set
History of character encoding
Assic -->Gb2312 ->gbk1.0-->gb18030
Assic -->unicode -->utf-8 /utf-16
Python2.x == Assic default encoding
#!-*- coding:utf-8 -*-
#coding:utf-8
python3.x == unicode default encoding
unicode is backward compatible gb2312, gbk
7 comments
Note
Single-line comments with a #
Multi-line comments three by three single or double quotes '' ' content annotated ' ''
8, user input
Input all the data received are strings, times you enter a number, but it will still be treated as a string
Int integer = integer string converted to int , with int (data is transferred)
Str string = string converted into the data string STR (data to be transferred to)
Expression if ... else statement
age_of_princal = 56
guess_age = int(input(">>:"))
'''
if guess_age == age_of_princal then
print("yes")
else print("no")
'''
if guess_age == age_of_princal:
print("yes,you got it..")
elif guess_age > age_of_princal:
print("shoud try samller..")
else:
print("try bigger..")
Indent error IndentationError: expected an indented block
^
IndentationError: unindent does not match any outer indentation level
SyntaxError: invalid syntax syntax error
tab! = (not equal to) 4 spaces
Indentation level must be consistent