04_ built-in function (ii)

Built-in Functions (ii) 1.1 callable ()

Function: Whether the function can be called

Example 1:

Def f1 ():    passf1 () F2 = 123f2 () # Output result typeerror: ' int ' object is not callable

Example 2:

Def f1 ():    pass# f1 () F2 = 123# F2 () print (callable (F1)) print (callable (F2)) # output result TrueFalse

1.2 Chr ()

Function: Digital to letter, return the corresponding ASCII code.

R = chr (+) print (r) # output result A

1.3 Ord ()

Function: Letter to Number

n = Ord ("B") print (n) # output 66

1.4 Range ()

Function: Range of values

Example 1: Randomly generated 6-bit CAPTCHA letters

# before using, you must import Randomimport  random# define an empty list Li = []# loop 6 times, value range 6 bit for I in range (6):    # Set random number range 65-91    temp = Random.rand Range (p, p)    # The generated number is converted to the letter     C = chr (temp)    # Adds the resulting results to the list Li inside    li.append (c) # li = ["C", "B", "a"  ] #cba  Merge # stitching string joinresult = "". Join (LI) # Print results printed (result)

Example 2: Random 6-bit Verification code full version letter + number

# before using, you must import Randomimport  random# define an empty list Li = []# loop 6 times, value range 6 bit for I in range (6):    # Set R to Random generation, range 0-5    r = Random.ran  Drange (0, 5)    # when r=2 or r=4 if    r = = 2 or r = = 4:        # num is 0-10 randomly generated        num = Random.randrange (0, ten)        # Add num value to list        li.append (str)    # when r=0,1,3,4    else:        # temp is a A-Z random number 65-91        temp = Random.randrange (+)        # conversion Gets the number to the letter        C = chr (temp)        # Add letter to List        li.append (c) # li = ["C", "B", "a"]  #cba  Merge # stitching string joinresult = "". Join (LI) # Print results printed (result)

1.5 Compile ()

Function: Compiling a string into Python code

# single Line # eval expression # exec pythons = "Print (123)" # Compile string into Python code r = Compile (s, "<string>", "exec") # Execute code exec (r) # lose Results 123

1.6 eval ()

Function: Executes an expression, gets the result, has a return value

s = "8*8" ret = eval (s) print (ret) # output 64

1.7 exec ()

Function: Execute python code, receive code or string, no return value

EXEC ("7+9+8")

Summary: Compile,exec,eval

Compile (): Convert, string, compile into Python code
Eval (): Executes an expression, gets the result, has a return value
EXEC (): Execute Python code with no return value

1.8 Dir ()

Features: Quickly see what features an object provides

# The View list provides which features print (DIR (list)) # output results [' __add__ ', ' __class__ ', ' __contains__ ', ' __delattr__ ', ' __delitem__ ', ' __dir__ ', ' __doc__ ', ' __eq__ ', ' __format__ ', ' __ge__ ', ' __getattribute__ ', ' __getitem__ ', ' __gt__ ', ' __hash__ ', ' __iadd__ ', ' __ Imul__ ', ' __init__ ', ' __iter__ ', ' __le__ ', ' __len__ ', ' __lt__ ', ' __mul__ ', ' __ne__ ', ' __new__ ', ' __reduce__ ', ' __reduce_ ' Ex__ ', ' __repr__ ', ' __reversed__ ', ' __rmul__ ', ' __setattr__ ', ' __setitem__ ', ' __sizeof__ ', ' __str__ ', ' __subclasshook_ ' _ ', ' Append ', ' clear ', ' copy ', ' Count ', ' extend ', ' index ', ' Insert ', ' pop ', ' remove ', ' reverse ', ' sort ']

1.9 Help ()

Features: View Help, feature details

1.10 Divmod ()

Function: Compare x, Y, return quotient and remainder, return type is tuple

Example: Total: 97, each page shows 10, how many pages need

R = Divmod (97,10) print (r) # Output results (9, 7) 

1.11 Isinstance ()

Function: Used to determine whether an object is an instance of a class

# object is an instance of class S = "Alex" R = isinstance (S, str) print (r) # output True

1.12 Filter ()

Function: Used to filter some elements in a list

Format: Filter (function, object that can be iterated)

Example: Li = [11, 22, 33, 44, 55,], filtering for more than 22

1.12.1 writing functions

# define function F1def F1 (args):    # Set Empty list    result = []
    # for loop for    item in args:        # To determine if item is greater than        $ if item >:            # greater than 22 added to result list            Result.append (item)    # Returns the result value return    Resultli = [11, 22, 33, 44, 55,]# execute function ret = f1 (LI) print (ret) # output [33, 44, 55]

1.12.2 Filter function

# define function F2def F2 (a):    if a >: return Trueli = [One, three, three, seven, three,        ]# filter Inner Loop The second parameter, let each loop element execute the function if the function's return value Tru E, element legal ret = filter (F2, Li) print (list (ret)) # output result [33, 44, 55]

The 1.12.3 is implemented with a lambda expression

Lambda Review Auto return

F1 = Lambda a:a > 30ret = f1 (All) print (ret) # implements filtering, simplified expression li = [one, one, a, a, a, a,]result = filter (lambda  a:a > , Li) Print (list result) # output [33, 44, 55]

1.13 Map ()

Function: Map a list to another list

Format: Map (function, iterative object (something that can be looped))

example, the number of tables in the list increased by 100 respectively

Map method

# list li = [11, 22, 33, 44, 55,]# define function F2, parameter adef F2 (a):    # function body, a + 100 and return value returns    A + 100# run function, all elements in Li list loop as parameters of F2 function A and execute Fresult = Map (F2, Li) print (list result) # output [111, 122, 133, 144, 155]

Lambda method

Li = [111, 122, 133, 144, 155]]result = map (lambda a:a + P, Li) print (list result) # output

1.14 globals (), locals ()

Globals all global variables

Locals all local variables

NAME = "ALEX"  # global Variable def show ():    a = 123  # local variable    c = 123    print (Globals ())    print (Locals ()) show () # Output result # global variable {' __cached__ ': None, ' __name__ ': ' __main__ ', ' __package__ ': None, ' __loader__ ': <_frozen_importlib_ External. Sourcefileloader object at 0x000000db870c5940>, 'NAME ': ' ALEX ', ' show ': <function show at 0x000000db8712e510>, ' __file__ ': ' old_dict.__delitem__ (host) \n\nprint (u "= = Information updated = =") \nprint (old_dict) \ n '} # local variable {' A ': 123, ' C ': 123}

1.15 Hash ()

Function: Convert hash value, commonly used to save key in dictionary

s = "FFFF" Print (hash (s)) # output 6225191154271087305

1.16 Len ()

Function: Character length

Python 3 default by character ()

s = "Li Jie" print (len (s))

python2.7 by default in bytes

s = "Li Jie" b = bytes (s, encoding= "Utf-8") print (len (b))

1.17 sum ()

Function: the addition of elements in a sequence of numbers

r = SUM ([11,22,33,44,]) print (r) # output 110

1.18 Memoryview ()

Description: A class of memory address-related

1.19 Object ()

Description: Is the parent class of all classes

1.20 Pow ()

Function: Method returns the value of XY (x's y-square)

# need to import Mathimport Mathprint (Math.pow (2, 3)) # Output Result 8.0

1.21 Property ()

Description: Attributes (object-oriented)

1.22 repr ()

Function: __repr__ in repr execution class

r = repr ("Alex") print (r) # output result ' Alex '

1.23 Reversed ()

Function: Invert

Print (List (reversed ([' NB ', ' is ', ' Alex ')]) # output results [' Alex ', ' is ', ' NB ']

1.24 round ()

Function: Rounding

Format: Round (number, reserved digits)

Print (Round (5.44, 1)) Print (Round (5.77, 1)) # output result 5.45.8

1.25 Slice ()

Features: Slicing

s = "Sssssssss" Print (S[0:2:2]) # output result s

1.26 sorted ()

Function: Sort

Li = [11, 44, 22, 33][11, 22, 33, 44] 33,]print (LI) li.sort () print (LI) # output results

1.27 Zip ()

Function: Accepts a series of iterated objects as parameters, packages the corresponding elements in the object into tuple (tuples), and returns a list of these tuples

L1 = ["Alex", one, one, one,]L2 = ["is", one, one, one,]l3 = ["NB", one, A, a,]r = Zip (L1, L2, L3) # Print (list (r)) temp = Lis T (r) [0]ret = "". Join (temp) print (ret) # Output results Alex is NB

　　

04_ built-in function (ii)