Inking Python notes (1): Basics

1. Type () to see the types of variables.

>>> Type (12.1)<class 'float'>>>> Type ('Hello')<class 'Str'>>>> Type (2)<class 'int'>>>> Type ('2')<class 'Str'>

2. Python 's variable names support numbers, letters, and underscores, but cannot start with a number.

3. expressions and declarations.

>>> n = 17>>> n17>>> 42+nprint(n)17

< Span style= "Font-size:small;" > + " *" +" can be used as a string connector, " *" multiple strings can be copied.

>>> first='throat'>>> second='Warbler' >>> first+Second'throatwarbler'Spam' 'spamspamspam'

5. Three types of errors in the program:

syntax error ; B. run-time error ; C. semantic error

int float< The span lang= "ZH-CN" > function converts integer data, numeric strings, and so on to floating-point types. str function to convert its arguments to strings.

 >>> Int ( " 2   '   '  2>>> int (5.67)  5 >>> Float (32)  32.0>>> float ( '   

< Span style= "Font-size:small;" >

 >>> import   math  >> > a=100>>> b=10>>> ratio=a/b  >>> print  (10*math.log10 (ratio)) #  log10 ()  10.0>>> print  (Math.log (MATH.E)) #  log ()  1.0>>> math.exp (Math.log (10))  10.000000000000002>>> radians=0.7>>> print  ( Math.sin (radians)) #  sin (), or cos (), tan ()  0.644217687237691>>> math.sqrt (4)/21.0 

8. Definition of function, note that the function must be defined before the function is called

>>>defPrint_lyrics ():#Define a functionPrint("i ' am a lumberjack, and I ' M okay.")Print("I sleep all night and I work all day")... ... ...>>> type (print_lyrics)#View Type<class 'function'>>>> Print_lyrics ()#perform the defined functionI'am a lumberjack, and I'm okay. I Sleep all Night andI work all day>>>defRepeat_lyrics ():#defines a function that contains a function that has already been defined... print_lyrics () ... print_lyrics ( ) ...>>>repeat_lyrics () I'am a lumberjack, and I'm okay. I Sleep all Night andI work all Dayi'am a lumberjack, and I'm okay. I Sleep all Night andI work all day

9. functions with parameters

>>>defPrint_twice (Bruce):#define a function that prints two times... Print(Bruce) ...Print(Bruce) ...>>> Print_twice ('Spam'*) Spamspamspamspamspamspamspamspam>>>Print_twice (Math.Cos (Math.PI))-1.0-1.0>>> michael='Eric, the half a bee'>>>Print_twice (Michael) Eric, the half a beeeric, the half a bee>>>defCat_twice (PART1,PART2):#defines a function that calculates "sum" of two input parameters. .. cat= Part1 +part2 ... print_twice (cat) ...>>> Cat_twice ()33>>> Cat_twice ('Hello',' World') Helloworldhelloworld

The return value of the void function is None.

>>> result=print_twice ('Bing') bingbingprint(Result ) None

Inking Python notes (1): Basics