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Just a simple factorial program I made in Python 3.

Python, 14 lines
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def fact():
    number=eval(input("Enter a number to get the factorial: "))
    initialvalue=1
    if number>0:
        for number in range(number,1,-1):
            initialvalue=initialvalue*number
        print(initialvalue)
    elif number==0:
        print(1)
    elif number<0:
            for number in range(number, -1, 1):
                initialvalue=initialvalue*number
            print(-initialvalue)
fact()

Should work with positive and negative numbers. Returns 1 for the factorial of 0 as it should.

2 comments

Steven D'Aprano 7 years, 8 months ago  # | flag

You make the very common mistake of using eval() on untrusted input. Just about everything I write here: http://code.activestate.com/recipes/578847-simple-derivative-solver-in-python/?in=lang-python#c1 applies to your code as well, except you should use int rather than float. So rather than repeat myself, I'll just ask you to read my comment there.

Hamid Sadeghi 5 years, 10 months ago  # | flag

I have a code too but just in 12 lines, and it works for any input, integer, float,and strings.and also I suppose 0!= 0 and for float numbers it calculate the factorial of it's integer part of the decimal number and for strings it prints some warning.

def factorial(n):

result = 1

if n == 1 or n== -1 or n==0:

result = n

else:

result = n * factorial(n-int((n/abs(n))))

return result

# #

try:

n=int(float((input("Enter a number to get the factorial: "))))

print(factorial(n))

except:

print("must be a number !!!")")

Created by John on Sat, 8 Mar 2014 (MIT)
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