Python basics_byseyOrd

Input and output

1) Input

　　Use input ("prompt information input")　

2) Output

　　print ("output content")

　　print ("% s% d"% ("Output is", 99))

type of data　

1) There are six types of python data types

• Number
• String
• List
• Tuple (tuple)
• Set
• Dictionary

2) Data type initialization

　　Python will automatically identify the data type and initialize when data is assigned

• Number num = 0
• String str = "asd"
• List list = [1,2,3]
• Tuple（元组）              tup = (1,2,2)         #tup = (1,)
• Set (set) set = {1,2,2,3} #equivalent to {1,2,3}
• Dictionary（字典）        dic = {"num1":"ren1","num2":"ren2","num3":"ren3"}

3) Methods of commonly used data types

List

Range (5) # Create a list of less than 5 [0,1,2,3,4] 
for I in Range (5 ):
     Pass

 

Tuple

= TUP (1,2,2 ) 
T1, T2, T3 = TUP # tuple access

def c (* x):    # pass what to define what 
    print (* x) 
x = (1,2,3 ) 
c ( * x) # * x is equal to break up tuples, then pass the parameter 
1 2 3 def c ( the X-*):    # pass What is the definition of what Print (the X-) 
c ( * the X-) 
( , 2, 3)


    

Dictionary

# Dictionary traversal two ways 
# for I, V in av_catalog [ 'Western'] .items (): # print key value and key 
#      Print (I, V) 
for I in av_catalog:
     Print (I, av_catalog [ i])

4) Variable type and immutable type

• Immutable data (3): Number (number), String (string), Tuple (tuple)
• Variable data (3): List (List), Dictionary (Dictionary), Set (Collection)

Control statement

 1）for

　　Statement format　

for i in [1,2,3 ]:
     pass 
for i in range (3 ):
     pass 
# range is a list generator

2）while

n = 1
while n < 11:
     if n == 7:
         pass
     else:
         print(n)
     n = n+1

3）break和continue   

continue means to jump out of the current loop and no longer execute the following code

break means to jump out of the entire loop

4) if statement

format

if   condition:
     pass 
elif :
     pass 
else :
     pass

5) Python's ternary operator

format

When the result of true if the determination conditions else is false results  

example

1 if 5> 3 else 0 
output 1, if 5 is greater than 3, otherwise output 0

Use in a list with for

= the conf (11,2,3 ) 
[I for I in the conf IF I> 2 ]
 >>> [. 11,. 3 ]
 # obtain a list of the number of qualifying

= the conf (11,2,3 ) 
[I for I, C in the enumerate (the conf) IF C> 2 ]
 >>> [0, 2 ]
 # obtain a qualified list index number 
# I, in the enumerate C (conf) Can get subscript and value at the same time