Is it possible to add int with str composed of text and numbers in Python?

Question

I asked that question Why in PHP the expression "2 + '6 apples'" is 8? here for finding this behavior strange.

And in the case of python?

I can convert the string '1' str for 1 int.

Example:

1 + int('1') # Imprime: 2

But if I try to convert '1 cachorro' str for int ...

int('1 cachorro');

... an error is generated:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '1 cachorro'

It would be possible to make expressions of the type 1 + int('1 cachorro') function in python?

If I needed to do this (I think I’ll never need to), how could I treat this case?

Answer 1

It would be possible to make expressions of the type 1 + int('1 cachorro') work in python?

Not. Or you sum whole or concatenate strings. This is part of Python type security.

If I needed to do this (I think I’ll never need to), how could I treat this case?

The only reasonable operation would be the concatenation of strings. If you want to add an integer to a string in places where Python has located numbers - which would be the most exotic interpretation of your question -, you would have to write your own function to accomplish this, and would not be using the sum operator.

Answer 2

Your question already has one reply in the English version of Stackoverflow!

The operator '+' works like this:

• If the 2 operands are numbers: add

• Else: concatenates strings.

If the string contains only numbers it can convert to integer.. otherwise gives an Exception.

Therefore, in the code where you want to convert a string to int you must "wait" for an exception to happen.

string = "abcd"
try:
    i = int(string)
    print i
except ValueError:
    #Trata a exceção
    print 'a string não é um número'

Answer 3

To do what you want, I think you can do the following:

int( re.search(r'\d+', '1cachorro).group() )

What this will do is take the string you placed, search the integer and return it. Then you can use this value to add it up.