Safe casting in python

Question

How to do safe cast in python

In c# I can safe cast by keyword as, e.g.:

string word="15";
var x=word as int32// here I get 15

string word="fifteen";
var x=word as int32// here I get null

Has python something similar to this?

Answer 1

Think not, but you may implement your own:

def safe_cast(val, to_type, default=None):
    try:
        return to_type(val)
    except (ValueError, TypeError):
        return default

safe_cast('tst', int) # will return None
safe_cast('tst', int, 0) # will return 0

Answer 2

I do realize that this is an old post, but this might be helpful to some one.

x = int(word) if word.isdigit() else None

Answer 3

I believe, you've heard about "pythonic" way to do things. So, safe casting would actually rely on "Ask forgiveness, not permission" rule.

s = 'abc'
try:
    val = float(s) # or int 
    # here goes the code that relies on val
except ValueError:
    # here goes the code that handles failed parsing
    # ...       

Answer 4

There is something similar:

>>> word="15"
>>> x=int(word)
>>> x
15


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


>>> try: 
...     x=int(word)
... except ValueError:
...     x=None
... 
>>> x is None
True