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

I. Problems brought before functional programming 1. The organizational structure of the code is not clear and the readability is poor. 2. When realizing repeated functions, you can only write code to realize functions repeatedly. The code is numerous and consumes time and energy. 3. If you need to expand or update some functions, you need to find out all the places to realize this function, modify them one by one, and you cannot manage them uniformly, which increases the difficulty of maintenance. 1. Functional formula encapsulates the code that realizes a certain function (code decomposition, loose coupling, division by function) 2, the function can achieve code reuse, thereby reducing the duplication of code writing 3, python function characteristics The parameters of a function can be any data type in Python, and the number of parameters can be zero or more. A function can also renege on any number of arbitrary data types in Python via the keyword return as a result. IV. Classification of functions

#Built-in function: URL as follows

https://docs.python.org/zh-cn/3.7/library/functions.html

For the convenience of development, for some simple functions, python interpreter has defined the functions as built-in functions, internal provides a lot of methods, common functions listed, similar to the shortcut created for reference convenience

For built-in functions, we can use them without implementing definitions, such as len(),sum(),max()

View built-in functions

s = dir(builtins)

print(s)

help()

dir()

vars()

type()

reload(temp) #Reload module

id()

is

#* coding:utf-8 *

"""

code comments

"""

l = [1, 2, 3]

a = 'aaa'

print(vars()) #All variables of the current module

print(file) #Current module file path strength

print(doc) #Document information for the current module

print(name) # python By default when executing.py files, name = main

import copy

print(copy.name) #value of script name executed main

identify who the main program is (program main file identification)

if name == "main":

pass

cmp()

abs()

bool()

divmod()

max()

min()

sum()

pow() **

len()

all() #Accepts a sequence, judges all values If true (empty), returns True Otherwise returns falsh

l = ['aaa','bbb']

all(l)

any() #if any is true, it is true

Practice all () any ()

--------------------------

chr() #ascii converts received digits to return characters

ord() #receives characters and returns numbers

hex() #hex

oct() #octal

bin() #binary

--------------------------

print(range(1,10)) #Generate an array

print(xrange(1,10)) #is a generator

for i in range(0, 100):

print i

for i in xrange(0, 100):

print i

The output of these two is the same, in fact, there are many differences, range will directly generate a list object:

a = range(0,100)

print type(a)

print a

print a[0], a[1]

Output:

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]

0 1

xrange does not generate a list directly, but returns one of its values each time it is invoked:

a = xrange(0,100)

print type(a)

print a

print a[0], a[1]

The results were as follows:

xrange(100)

0 1

enumerate()

l = [1,2,3,4]

for k,v in enumeratel):

print(k,v)

observation rule

for k,v in enumerate(l,1):

print(k,v)

Set the starting value V, custom function

Obviously, the functions that built-in functions can provide are limited. According to our own needs, we can customize our own functions in advance to achieve certain functions. Later, when encountering application scenarios, we can call custom functions.

#import function

6. Definition of function

1. How to customize functions?

The definition of a function may involve the following points:

def Function name (argument 1, argument 2, argument 3,...):

'''Comment''

function body

return The value returned

#The function name should reflect the meaning of the function itself def: The keyword that defines the function Function name: The name of the function, and later call the function body according to the function name: A series of logical calculations are performed in the function, such as: sending an email, calculating the maximum number in [11,22,38,888,2], etc... Parameters: provide data for the function body return: when the function is executed, it can return data to the caller. What does the function do in the definition phase?

Only the syntax required to define the function is detected, and the code within the function body is not executed

That is, syntax errors are detected at the function definition stage, while logical errors in code are only known at the time of call execution.

def get_result():

r - 1

get_result()

After calling the function, it will output the following error prompt result:

NameError: name 'r' is not defined

get_reuslt = """

r - 1

"""

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