如何在列表中存储信息

Question

My goal is to create a program that checks whether a number is a prime number and displays the total number of factors if it is not a prime number.

I have started the code but I realize I need to store my factors in a list in order for the number of factors to be displayed. Here is my (edited) Python code so far:

userNum = int(input("Enter a number: "))
print("User Number: ", userNum)

numFactors = []
for x in range(1, userNum+1):
       if(userNum % x == 0):
           factor = 0
           numFactors.append(x)
           factor = factor + 1
           print(userNum,"is not a prime number")
           print("Number of factors: ", factor)
           break
       else:
           print(userNum,"is a prime number")

Can someone please tell me how to continue with storing factors into my list (numFactors)? Thank You!

Answer 1

You need to use append()

Your syntax changed as below.

userNum = int(input("Enter a number: "))
print("User Number: ", userNum)
numFactors = []
for x in range(1, userNum+1):
       if(userNum % x == 0):
           factor = 0
           numFactors.append(x)
           factor = factor + 1
           ...
           ...

But there is a logical flaw in your code. Try input as 99 .

Corrected solution

userNum = int(input("Enter a number: "))
print("User Number: ", userNum)
numFactors = []

# A prime number (or prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself.
# Hence range starting from 2
for x in range(2, userNum+1):  
       if(userNum % x == 0):
           numFactors.append(x)
if len(numFactors) == 1:
    print(userNum, " is a prime number")
else:
    print(userNum,"is not a prime number")
    print("Number of factors: ", len(numFactors))
    print("Factors : ", numFactors)

Output

Enter a number: 99
User Number:  99
99 is not a prime number
Number of factors:  5
Factors :  [3, 9, 11, 33, 99]

Answer 2

First, you need to put the line that defines numFactors , numFactors = [] , outside of and before the for loop. Otherwise, it will be continually set to an empty list for each iteration of the loop.

Values can be added to the end of a list by using the list's append method. For example, numFactors.append(2) would add 2 to the end of the list.

Answer 3

Your mistake is lacking check whether x is equal to userNum, that is in the end of the loop.

My other suggestion is you remove variable factor as this can be known from the length of the numFactors list.

userNum = int(input("Enter a number: "))
print("User Number: ", userNum)
numFactors = []
for x in range(1, userNum + 1):
    if userNum % x == 0:
        numFactors.append(x)

    if userNum == x:
        print("Factors: " + str(numFactors))
        if len(numFactors) == 2:
            print(userNum, "is a prime number")
        else:
            print(userNum, "is not a prime number")
            print("Number of factors: ", len(numFactors))