AttributeError: 'int' object has no attribute 'isdigit'

Question

numOfYears = 0
cpi = eval(input("Enter the CPI for July 2015: "))
if cpi.isdigit():
    while cpi < (cpi * 2):
        cpi *= 1.025
        numOfYears += 1
    print("Consumer prices will double in " + str(numOfYears) + " years.")
while not cpi.isdigit():
    print("Bad input")
    cpi = input("Enter the CPI for July 2015: ")

I'm getting the following error.

AttributeError: 'int' object has no attribute 'isdigit'

Since I'm new to programming, I don't really know what it's trying to tell me. I'm using the if cpi.isdigit(): to check to see if what the user entered is a valid number.

Why not use `int(input(...))` which will convert string to int — sam, Oct 10 '15 at 01:02
Can you provide more information like What is the value you are passing? What is your python version? What is the stacktrace? — kingpin, Oct 10 '15 at 01:03
I'm entering an integer "239" but when someone else runs the program, they should be able to enter an int or a float. — Kristofer Ard, Oct 10 '15 at 01:04
Additional this code has a huge [Arbitrary code execution](http://en.wikipedia.org/wiki/Arbitrary_code_execution) vulnerability due to it `eval`ing user input, which could contain python code. — pppery, Oct 10 '15 at 01:08
This code will loop forever, unless `cpi` is negative, because a non-negative number is less than itself times two by basic rules of math. — pppery, Oct 10 '15 at 01:16
In the condition "while cpi < (cpi * 2)", is there any way I can get the number that the user enters to double its self without having an infinite loop? — Kristofer Ard, Oct 11 '15 at 01:30

marmeladze · Answer 1 · 2015-10-10T01:24:28.770

As documented here isdigit() is a string method. You can't call this method for integers.

This line,

cpi = eval(input("Enter the CPI for July 2015: "))

evaluates the user input to integer.

>>> x = eval(input("something: "))
something: 34
>>> type(x)
<class 'int'>
>>> x.isdigit()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'int' object has no attribute 'isdigit'

But if you remove eval method (you should better do that),

>>> x = input("something: ")
something: 54
>>> type(x)
<class 'str'>
>>> x.isdigit()
True

everything will be fine.

by the way using eval without sanitizin user input may cause problems

consider this.

>>> x = eval(input("something: "))
something: __import__('os').listdir()
>>> x
['az.php', 'so', 'form.php', '.htaccess', 'action.php' ...

But you still didn't explain what will happened when running `cpi *= 1.025` and `cpi` is `str`... — Remi Guan, Oct 10 '15 at 01:38
it will spit TypeError, then he will edit the question, and will ask "I have another issue" :) — marmeladze, Oct 10 '15 at 01:46

score 6 · Answer 2 · edited Jan 12 '18 at 10:51

6

Use this:

if(str(yourvariable).isdigit()) :
    print "number"

isdigit() works only for strings.

edited Jan 12 '18 at 10:51

clemens

16,716
11
50
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answered Jan 12 '18 at 10:29

usr_11

548
10
31

isdigit() will not work with negative numbers. It does not see the - as a digit and returns false. To solve that you can simply use this... yourString.replace("-","").isdigit() – Brént Russęll Mar 14 '19 at 02:37

score 4 · Accepted Answer · answered Oct 10 '15 at 01:26

numOfYears = 0
# since it's just suppposed to be a number, don't use eval!
# It's a security risk
# Simply cast it to a string
cpi = str(input("Enter the CPI for July 2015: "))

# keep going until you know it's a digit
while not cpi.isdigit():
    print("Bad input")
    cpi = input("Enter the CPI for July 2015: ")

# now that you know it's a digit, make it a float
cpi = float(cpi)
while cpi < (cpi * 2):
    cpi *= 1.025
    numOfYears += 1
# it's also easier to format the string
print("Consumer prices will double in {} years.".format(numOfYears))

score 0 · Answer 4 · edited May 23 '17 at 12:16

eval() is very dangerous! And int() built-in function can convert string to digit.

If you want to catch the error if user didn't enter a number, just use try...except like this:

numOfYears = 0

while numOfYears == 0:
    try:
        cpi = int(input("Enter the CPI for July 2015: "))
    except ValueError:
        print("Bad input")
    else:
        while cpi < (cpi * 2):
            cpi *= 1.025
            numOfYears += 1

print("Consumer prices will double in", numOfYears, "years.")

AttributeError: 'int' object has no attribute 'isdigit'

4 Answers4