Built-in functions day14 classroom summary

Pre-course review

Iterator

Iterator object must be iterable, iterables not necessarily iterator object

Iterables

Containing the __iter__data type of the method

In addition to numeric types are iterables

Iterator object

Containing the __iter__,__next__data type of the method

File is the iterator object

Iterables plus __iter__will become iterator object

Iterator object plus __iter__method is still the iterator object

for circulation principle

lt = [1,2]

lt_iter = lt._iter_()
while True:
    try:
        print(lt_iter._next_())
    except StopIteration:
        break

A triplet of expressions

Condition holds if condition else condition is not satisfied

List comprehensions

[i fo i in range(10)]

Dictionary of formula

{i:i for i in range(10)}

zip

A plurality of read iterables disposable objects each iteration of the elements, the elements makes up

Generator expressions

(I for i in range (10)) # save memory space - "Generator -" old hen

[I for i in range (10)] - "list -" a basket of eggs

Builder

Nature is an iterator, is custom iterators, function containing the yield keyword

def ge():
    yield

yield

1. Pause function
2. A yield value taken by the next

def range(start,stop,step):
    while start < stop :
        yield start
        start += step
        
        
for i in range(1,10,2):
    print(i)

Recursion

Function calls itself, there is an exit condition

count  = 0
def a():
    global count
    print(count)
    
    if count == 100:
        return
    count += 1
    a()
    
a()

Anonymous function

A named function

Before we given function are well-known function, which is based on the use of the function name.

Anonymous function

Anonymous function, he has no name binding, ie, once recovered, brackets to run.

Anonymous function syntax:

lambda Parameters: Return Value

f = lambda x, y:x * y
res = f(1,2)
print(res)

Built-in functions

python interpreter built-in method:

grasp:

1. bytes

res = bytes('中国',encoding='utf8')
print(res)

b'\xe4\xbd\xa0\xe5\xa5\xbd'

res = '你好'.encode('utf8')
print(res)

b'\xe4\xbd\xa0\xe5\xa5\xbd'

1. chr () / word ()

CHR () refer to a digital ASCII code table converted into a corresponding character; the ord () converts the character into a corresponding digital.

print(chr(65))

A

print(ord('A'))

65

1. divmod () columns

print(divmod(10,3)) #取整/取余

(3,1)

1. enumerate () iteration with indexes

l = ['a','b','c']
for i in enumerate(l):
    print(i)

(0,'a')
(1,'b')
(2,'c')

1. eval () translates into a string data type, the string is removed, the stay.

lis = '[1,2,3]'
lis_eval = eval(lis)
print(lis_eval)

[1,2,3]

1. hash () whether a hash, the variable type is not hashed

print(hash(1))

1

To understanding:

1. ABS () absolute value.

print(abs(-13)) # 求绝对值

13

1. all () within iterables elements are all true, then it returns true.

print(all([1,2,3,4]))
print(all([]))

Ture
False

1. any () iterables there is an element is true, True.

print(any([1,2,3,0]))
print(any([]))

True
False

1. bin () / oct () / hex () binary, octal, hexadecimal conversion.

print(bin(17))
print(oct(17))
print(hex(17))

0b10001
0o21
0x11

1. dir () of all the methods listed modules

import time 

print(dir(time))

1. frozenset immutable set () (non-set change, similar to the tuple)

s = frozenset({1,2,3})

frozenset({1,2,3})

1. globals () / loacals () view the global variables / variable view the current location

def func():
    s = 's1'
    print(globals())
    print('locals():',locals())

   
func()

locals():{'s':'s1'}

1. pow()

print(pow(3,2,3)) # (3**2)%3

0

1. round () rounding

print(round(10.33))

10

1. slice

lis = ['a','b','c']
s = slice(1,4,1)
print(lis[s])

['b', 'c']

1. sum()

print(sum(range(100)))

4950

1. __import__() Introduced into the module string

time = __import__('time')
print(time.time())

Exception Handling

Exception Handling: report a mistake, for processing

Abnormal capture can only capture logic error, not a syntax error

print(1)
num = input('请输入数字:')

try:
    1/int(num) # 报错之后，不运行下面的代码
except ZeroDivisionError:
    print('傻逼,不能输入0')
    
print(2)
    

except Exception as e: # 万能异常，只要有错误，就捕捉
    print(e) # 错误的描述信息

Process-oriented programming

" Process-oriented " (Procedure Oriented) is a process-centric programming ideas. "Procedure-oriented" may also be referred to as "record-oriented" programming ideas, they do not support rich "object-oriented" properties (such as inheritance, polymorphism), and they do not allow mixing and persistent state domain logic.

Is to analyze the steps required to solve the problem, then use the function to implement these steps, step by step, when used in a call to a turn on it.