Python Process Control

Python Process Control If-else statement

• Examples of IF statements:

if1<‘a‘:...     "chen"...chen

• The logical value (BOOL) is used to denote: right and wrong, true and false, empty and non-empty concepts.
• The logical value consists of two values:
  True: Indicates a non-empty amount (such as string,tuple,list,set,dictionary, etc.)
  False: Indicates 0,none, empty amount
• Function: Mainly used in judging statements, used to judge
  
  1. Whether a string is empty
  2. Whether the result of an operation is 0
  3. Whether an expression is available

"0"if a:...     "not null"...not null

0if a:...     "chen"...else:...     "ok!"...ok!

• Else statement can have more than one

#!/usr/bin/python  while  1 : x = Int (raw_input ()) if  x >= 90 : 
     
      print 
       "x >="  elif
      x >= 80 : print  " > x >= " elif  x >= 60 : print      "> x >="  else : print   "< 6 0 " break   
 

logical operators

• If the conditional statement after the IF, you can use And,or, or not
• And means two conditions are set up at the same time
• Or have a set up both can
• Inverse of Not condition value

>>>True  and FalseFalse>>>1  and 1  and 00>>>True or 0True>>>True or 0 or FalseTrue>>>True  and 0 or FalseFalse

For loop

>>> a = (1,3,4,78,12forin a:...     print i...1347812forin"ads87":...     print i...ads87

Range (I,j, step value)

Note :
I is the starting value, including
J is the terminating value, not included
(similar to slices)

forin range(1,4):...     print i...123

• The step values are shown below:

forin range(1,10,2):...     print i...13579

Range can produce a sequence:

range(10)[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Traverse Dictionary

>>> a = {1:11,2:22,3:33,4:44forin a:...     print i...1234

• As you can see, this iterates through the dictionary's key values, so you can access the dictionary by a[the key value].
• In fact, another method is also possible.

>>> A.items () [(1, One), (2, A), (3, -), (4, -)]>>> forIinchA.items ():...Print I...(1, One)(2, A)(3, -)(4, -) >>> forKey,valueinchA.items ():...Print key...Print value...1 One2 A3 -4 -

Loop control

• For also can be paired with else ~

forin range(10):...     pass...else:...     "end~"...end~

• What are the eggs for?
• Is that the content in else does not appear when the program is not performing properly. Or the break jumps out of the box and does not execute the contents of else.

>>> import time>>>  For  i in  range (10 ):      ...      Print I ...  Time.sleep (2 )  ...      else :  ...  Print  "OK"   ...  0  1  2  ^ctraceback (most recent call last): File  <stdin> ", line 3 , in  <module> Keyboardinterrupt  

forin range(10):...     if4:...         break...else:...     "end"...

• Break jumps out of the loop
• Continue end this cycle and enter the next cycle
• Exit () end the entire program
• Pass placeholder, equivalent to an empty statement

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Python Process Control