The factorial summation of Python's small code

Demand:

Factorial: Also a term in mathematics; factorial means multiplying from 1 times 2 times 3 times 4 to the required number; When expressing factorial, use "! "To express. such as h factorial, is expressed as h!; factorial is generally difficult to calculate, because the product is very large.

Question: Ask for 1+2!+3!+...+20! 's and

Implementation environment: Python3

Editor: Pycharm

Analysis: 1, factorial calculation is a more troublesome part of the implementation of recursive function is a better solution, first define a recursive function to achieve the factorial function.

def recursion (n): ' Define recursive function for factorial function ' if N==1:return 1else:return n*recursion (n-1)

2, summed up the idea, you can directly sum, you can also define a list to append the factorial result of the for traversal traversal to the list, and then use the sum () function to sum.

Sum_0=0print ("For loop directly calls recursive function summation". Center ("*")) #显示效果明显for I in Range (1,21): Sum_0 +=recursion (i) print (SUM_0) list sum scheme: l Ist=[] #定义一个空的列表, append the factorial value generated by the calling recursive function to the list print ("Write 1-20 factorial to the list, sum with the SUM function". Center ("*") #显示效果明显for I in Range (1,21): list. Append (recursion (i)) # appends the factorial value generated by the calling recursive function to the list print (SUM (list) #列表求和两者代码行数一样多都可以实现其功能.

Use knowledge points: Recursive functions for loop range () functions, and so on.

Full source code and results:

#/usr/bin/env python#_*_coding:utf-8_*_def  recursion (n :     ' definition of recursive function for factorial function '     if n==1:         return 1    else:         Return  n*recursion (n-1) list=[]  #定义一个空的列表, append the factorial value generated by the calling recursive function to the list print ("Write the factorial of 1-20 to the list, sum with the SUM function.") Center ("*")   #显示效果明显for   i  in range (1,21):     List.append (recursion (i)) #  appends the factorial value generated by the calling recursive function to the list print (sum (list))   #列表求和sum_0 =0print ("The For loop calls the recursive function sum directly.") Center ("*")   #显示效果明显for   i  in range (1,21):     sum_0  +=recursion (i) print (SUM_0) Result: ***************************** writes the factorial of 1-20 to the list, using the SUM function to sum ************************ 2561327494111820313********************************for Loop Direct call recursive function summation ********************************* 2561327494111820313 

Both are verified to achieve basic functionality, but the calculation of larger amounts of data is not tested.

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The factorial summation of Python's small code