名称“USER_INPUT”未定义？ （Python 3.9.2）

Question

I'm trying to make a Python program which takes in a string and evaluates whether it's a palindrome (reads the same backwards) or not. I've tried to extend it by not allowing numbers to come as an input, and that part works fine.

a = eval(input('Put a word here: '))

if type(a) == int or float:
    print('That\'s a number man.')
    exit()

b = a[::-1]
if a == b:
    print('The word is a palindrome!')
else:
    print('The word is not a palindrome!')

However, when I run the program with a random word, such as 'fries', as an input in cmd (using Windows, Python 3.9.2), I get this error:

Traceback (most recent call last):
  File "C:\Users\Azelide\Desktop\folderr\hello.py", line 1, in <module>
    a = eval(input('Put a word here: '))
  File "<string>", line 1, in <module>
NameError: name 'fries' is not defined

I've seen people getting this error when running Python 2 and using input() instead of raw_input(), that should not be a problem in Python 3 though. By the way, when I omit the part of the code which excludes numbers from the input, the palindrome checker works fine. Any ideas?

Answer 1

As mentioned in the comments, your first condition always evaluates to true

try this:

a = input('Put a word here: ')

for char in a:
    if char.isdigit():
        print('That\'s a number man.')
        exit()

b = a[::-1]
if a == b:
    print('The word is a palindrome!')
else:
    print('The word is not a palindrome!')

output:

Put a word here: fries
The word is not a palindrome!

Answer 2

I have managed to solve it now, while extending it to not allow number-letter combinations.

a = input('Put a word here: ')

try:
    float(a)
    print('That\'s a number man.')
    exit()
except ValueError:
    for char in a:
        if char.isdigit():
            print('That\'s a combination of letters and numbers.')
            exit()

b = a[::-1]
if a == b:
    print('The word is a palindrome!')
else:
    print('The word is not a palindrome!')

Answer 3

I will tell you what is wrong in your code the function eval takes a string so that if the string could be a function it will make the function else it will raise error and when you made the function input inside it, this returns a value if this value == a function then make the function else raise error like this

a = eval(input('enter a name: '))

now if the user enters a value which can not be a function it will raise error like this

name'value that the user input' is not defined

now you can make as what the people said up

a = input('Put a word here: ')

try:
    float(a)
    print('That\'s a number man.')
    exit()
except ValueError:
    for char in a:
        if char.isdigit():
            print('That\'s a combination of letters and numbers.')
            exit()

b = a[::-1]
if a == b:
    print('The word is a palindrome!')
else:
    print('The word is not a palindrome!')