Shulou(Shulou.com)06/02 Report--

In this issue, the editor will bring you an example analysis of the built-in functions of python. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Range function

Be able to generate a specified sequence of numbers

Use case:

'' range (start,stop,step) parameter: start: start value, default value is 0 stop: end value step: optional, step value default value is 1 return value: iterable object, number sequence''# range function is used # write only one parameter, that is, from zero to before 10, 9 res = range (11) # when two parameters, the first parameter is the start value The second parameter is the value of the end (before the end value) res = range (5Power10) # three parameters, parameter 1 is the start value, parameter 2 is the end value, parameter 3 is the step value res = range (1Magazine 10Cool 3) # get a flashback number sequence res = range (10memo 0lame 1) res = range (10cor 0lim 2) res = range (- 10flint 20lim 1) res = range (- 20Lint 10) res = range (- 10L10) print (list (res))

The method of extracting the sequence of numbers returned by the range () function:

# the method of getting the sequence of numbers returned by the range function res = range (10)

List list data

Print (list (res))

Traversing through a for loop

For i in res: print (I)

Turn to an iterator and use the next function to call

Res = iter (res) print (next (res)) print (next (res)) zip () function

The zip function accepts multiple iterable objects, and then combines the I th element of each iterable object to form a new iterator.

Example:

Parameter: * iterables, any iterable object

Return value: an iterator that returns a tuple

Var1 = '1234'var2 = [' axiaojia'] var3 = (''axiomagy,''B',')

Call the zip function to form a new tuple iterator

Res = zip (var1,var2,var3) # print (res,type (res)) for i in res: print (I)''('1','a','A') ('2','b','B') ('3','C','C') ('4','d','D')''

Zip (), combined with the * operator, can be used to disassemble a list:

X = [1,2,3] y = [4,5,6] zipped = zip (x, y) print (list (zipped)) print (zip (x, y)) # iterator object, print (* zip (x, y)) # combined multiple tuple data other built-in functions

Built-in functions related to data type conversion

Int () converts other types of data to integers

Float () is converted to a floating point type

Bool () converted to Boolean type

Complex () becomes plural

Str () converted to string type

List changes to list type

Tuple is converted to tuple type

Dict changes to dictionary type

Set is converted to collection type

Variable correlation function

Id () gets the ID identity of the current data

Type () gets the type string of the current data

Printing of print () data

Input () gets the input data

Isinstance () detects whether it is the specified data type

Mathematical correlation function

#

Get the absolute value of a number print (abs (- 99.9999)) # Sum the items in iterable from left to right from start and return the total value print (sum ([1MJ 2) 3]) # get the maximum print (max ([1J 2J 3])) print (max (99J 12) 45) # get the minimum value print (min ([2Q 1J 6 Lok 9])) print (min (6 Mol 7 Jo 1 Jue 0) (- 2)) # the power operation returns the y power print of x (pow (2p3)) # rounded r = round (3.1415926) r = round (3.1415926) # the decimal point retains several digits r = round (4.5) # odd forward and even backward 1. 5 = 22. 5, 2, 3, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 4, 4, 4, 2, 4, 4, 4, 4, 2, 2, 4, 4, 4, 2, 4, 4, 2, 4, 4, 4, 4, 5, 4, 4, 4, 2, 2, 4, 4, 4, 2, 4, 4, 4, 4, 4, 2, 4, 4, 2, 4, 4, 4, 4, 5, 4, 4, 4, 2, 4, 4, 4, 2, 4, 4, 5, 4, 4,

# bin () convert numeric types to binary print (bin (123)) # 0b1111011# int () convert binary to integer print (int (0b1111011)) # 123 # oct () to octal numbers 01234567 print (oct (123)) # 0o173# hex () to hexadecimal numbers 0123456789abcdef print (hex (123)) # 0x7b# convert characters to asciir = ord ('a') print (r) # convert ascii to words Sign r = chr (65) print (r) higher order function

Sorted (iterable, [reverse,key])

Take out the elements in the iterable data one by one, put them into the key function for processing, and sort them according to the results of return in the function to return a new list.

Function: sorting

Parameters:

Iterable iterable data (container type data, range data sequence, iterator)

Reverse is optional. Whether to reverse or not. Default is False. No reversal, True reversal.

Key optional, function, can be a custom function or a built-in function

Return value: sorted result

Arr = [3, 7, 1, 1, 9, 20, 10]

Sort from small to big by default

Res = sorted (arr) # [- 9,1,3,7,10,20]

Can be sorted from large to small

Res = sorted (arr,reverse=True) # [20,10,7,3,1,-9]

Use the function abs (absolute value) as the key keyword parameter of sorted

Res = sorted (arr,key=abs) print (res)

Use custom functions

Def func (num): print (num,num% 2) return num% 2 arr = [3, 2, 4, 6, 5, 7, 9]

Use custom functions to process data in sorted functions

Res = sorted (arr,key=func) print (res) # optimized version arr = [3, arr,key=lambda x:x%2, 4, 5, 7, 9] res = sorted (arr,key=lambda x:x%2) print (res) map (func, * iterables)

Each element in the incoming iterable data is put into the function for processing and a new iterator is returned.

Parameters:

Func function Custom function | built-in function

Iterables: iterable data

Return value: iterator

(1) convert a list of string numbers into a list of integers

# [1] for i in varlist: newlist.append (int (I)) print (newlist) the common method of handling is varlist = [1, 2, 2, 4, 4, 5, 5, 4, 3, 4, 4, 3, 4, 5, 4, 5, 5, 5, 4, 5, 4, 5, 4, 5, 4, 5, 4, 4, 4, 3, 4].

Use the map function for processing

Varlist = ['1] res = map (int,varlist) # print (list (res))

(2) [1, 2, 3, 4] = > [1, 4, 4, 9, 16]

Common method

Varlist = [1Jing 2 Jing 3 Jing 4] newlist = [] for i in varlist: res = I * * 2 newlist.append (res) print (newlist)

Use the map function to process this data

Varlist = [1 myfunc,varlist 2 3 varlist 4] def myfunc (x): return x * * 2 res = map (myfunc,varlist) print (res,list (res))

Optimized version

Res = map (lambda XRV x Varlist) print (res,list (res))

Practice homework

['axiaqingmei'] = > [65pd6 / 67pm68]

Reduce (func,iterable)

Each time we take two elements from iterable and put them into the func function to get a calculation result, and then put the calculation result and the third element in iterable into the func function to continue the operation, and the result and the fourth element after that are added to the func function for processing, and so on, until the final element is involved in the operation.

Parameters:

Func: built-in or custom functions

Iterable: iterable data

Return value: the final operation result

Note: when using the reduce function, you need to import from functools import reduce

From functools import reduce

(1) [5, 2, 1, 1] = > 5211

Common method

Varlist = [5 for i in varlist: res + = str (I) res = int (res) print (res,type (res)) '521 15 * 10 + 2 = = 5252 * 10 + 1 = 521521 * 10 + 1 = = 5211

Using reduce to complete

Def myfunc (XMague y): return x*10+yvarlist = [5 mine2 pyrrine 1]

Call function

Res = reduce (myfunc,varlist) print (res,type (res))

(2) change the string's' 456'= > 456

How to solve the above problem when it is required that the int method cannot be used for type conversion

Define a function that returns an integer number given the number of a string

Def myfunc (s): vardict = {# # * * $$} {0 # # * * $$} 10: 1 return vardict (s): 5: 5: 6: 7: 7: 8: 8: 9]

First use the map function to convert a numeric string into an integer number.

Iter1 = map (myfunc,'456')

Use lambda to reprocess the values in the number list

Iter2 = reduce (lambda x print (iter2) filter (func,iterable)

Filter the data, take each element in iterable to the func function for processing, retain the data if the function returns True, and discard the data if False is returned.

Parameters:

Func custom function

Itereble: iterable data

Return value: an iterator of retained data

It is required to keep all even numbers and discard all odd numbers.

Varlist = [1, 2, 3, 4, 5, 6, 7, 8, 9]

Common method implementation

Newlist = [] for i in varlist: if I% 2 = 0: newlist.append (I) print (newlist)

Use filter for processing

Define a function to determine whether the current function is even. Even returns True and odd returns False.

Def myfunc (n): if n% 2 = 0: return True else: return False

Call the filter function to process

It = filter (myfunc,varlist) print (it,list (it))

Optimized version

It = filter (lambda n:True if n% 2 = = 0 else False,varlist) print (it,list (it)) the above is the example of python built-in function that Xiaobian shared with you. If you happen to have similar doubts, please refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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