2021-03-04 comp9021 class 6 notes

review

1. Get the ASCII code
   

2. Sort
   
   

3. lambda expression
   
   
   

Classic questions - Prime factor - Prime Factor

Give a positive integer , Print out the prime factor of the number .
I don't know what a prime factor is , Look here Prime factor , Prime factor .

from math import sqrt

def primeFactors(m):
    '''return the prime factors of the input number m '''
    prime_factors = [] #  Used to store prime factors 
    factor = 2 #  The smallest prime factor 
    upper_bound = int(sqrt(n)) #  The upper limit of the factor of a number 

    while factor <= upper_bound: #  from 2 Start traversing to the upper limit 
        while m % factor == 0:  #  Determine whether the current value is a factor 
            m //= factor
            prime_factors.append(factor)
        factor += 1
    if m != 1:#  If the last number is not 1, Then this number is also a prime factor  #  Thanks for the reminder from wow le , Modified here 
        prime_factors.append(m) #  Put yourself in the results 
    
    prime_factors = [str(x) for x in prime_factors]
    return f"{n} = {'*'.join(prime_factors)}"

n = 231084
print(primeFactors(n))

Number of statistical prime factors

from math import sqrt

def primeterFactorInfo(m):
    prime_factors = {
    }
    factor = 2
    upper_bound = int(sqrt(n))

    while factor <= upper_bound:
        while m % factor == 0:
            m //= factor
            if factor not in prime_factors:
                prime_factors[factor] = 1
            else:
                prime_factors[factor] += 1
        factor += 1
    if m != 1:#  If the last number is not 1, Then this number is also a prime factor  #  Thanks for the reminder from wow le , Modified here 
        prime_factors[m] = 1
    return prime_factors
        
n = 5432
primeterFactorInfo(n)

Count the number of prime factors collections.counter

Precision problem - precision

A reminder from Mr. Luo ：
This round It's not round off as mentioned above , Sometimes I give up and sometimes I go in , It is python The precision of the decimal representation of itself .
The test and official documentation are as follows

• Test accuracy
  
  The following code is the result of each line ( Except for the equation ） All output , and matlab almost .

from IPython.core.interactiveshell import InteractiveShell
InteractiveShell.ast_node_interactivity = 'all'

Calculation n The prime number within

Calculate program run time

• timeit modular
  Official documents ：timeit - Calculate the running time of a small code module
  
• globals function
  globals The function returns all global variables of the current environment . stay timeit This function can avoid the trouble of manually entering parameters .
  Official documents ： At the bottom of the page , the last one
  Use... In the program ：