Python Basics Quick Learn-hello.py

1 #Coding=utf-82 3 #hello.py python learning start4 5 #====== Comment ======6 #Python uses the # notation to mark annotations7 8 #One comment9 Print 'Hello world!'Ten  One #====== operator ====== A #Arithmetic Operators - #self-Increment 1-decrement 1 operator not supported - #* * Indicates the highest priority of the exponentiation the Print-2*4 + 3**2 -  - #comparison operator returns a Boolean value (True/false) - Print2 < 4; + Print6.2 > 6.2001 -  + #A logical operator joins any expression together to return a Boolean value A Print3 < 4 and4 < 5 at Print  not6 <= 6.2 - Print2 > 4or2 < 4 -  - #====== variable ====== - #no need to pre-declare variable types -Count = 10 in Print "count is%d"%(count) -  to #====== string ====== + #define string single or double quotation marks (three quotation marks can be used to contain special characters) -Pystr ='Python' theIscool ='is cool!' * #String Connection $ PrintPystr +' '+IscoolPanax Notoginseng  - #index: [] Slice: [:] the #Index rule: The index of the first character is 0, the last character index is -1 + PrintPystr[0] A PrintPystr[2:5] the PrintIscool[:2] + PrintIscool[3:] - PrintIscool[-1] $  $ #====== list ====== - #list elements with [] package number and value can be changed - #operations like arrays can be indexed and sliced theAlist = [1, 2, 3, 4] - PrintalistWuyi PrintAlist[0] the  - #====== tuple ====== Wu #tuple elements with () package number and value can not be changed - #operations like arrays can be indexed and sliced AboutAtuple = ('Robots', 77, 93,'Try') $ PrintAtuple - PrintAtuple[:3] -  - #====== Dictionary ====== A #The mapping data type is composed of key-value (key-value) pairs + #The dictionary element is wrapped with {} theAdict = {'Host':'localhost'} - Printadict $adict['Port'] = 8080 the PrintAdict.keys () the Printadict['Host'] the  the #====== control Operation ====== - #keyword followed by expression ': ' End inx =-1 the ifX <. 0: the     Print '"X" must be atleast 0!' About  theCount =0; the  whileCount < 3: the     Print 'Loop #%d'%(count) +Count + = 1 -  theFoo ='ABC'Bayi  forCinchfoo: the     PrintC the  - #====== List parsing ====== -squared = [x**2 forXinchRange (4)] the  forIinchSquared: the     PrintI the  the #====== function ====== - #The definition function consists of the def keyword and its subsequent function name, plus the required function parameters ': ' End the #function parameters can define a default value the defaddme2me (x): the     'Apply + operation to argument'94     return(x +x) the  the PrintAddme2me (4.25)

Python Basics Quick Learn-hello.py