Convert a string to integer with decimal in Python

Question

I have a string in the format: 'nn.nnnnn' in Python, and I'd like to convert it to an integer.

Direct conversion fails:

>>> s = '23.45678'
>>> i = int(s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: '23.45678'

I can convert it to a decimal by using:

>>> from decimal import *
>>> d = Decimal(s)
>>> print d
23.45678

I could also split on '.', then subtract the decimal from zero, then add that to the whole number ... yuck.

But I'd prefer to have it as an int, without unnecessary type conversions or maneuvering.

Matt, 23.45678 isn't an integer. If you want Python to convert a string to an integer, make sure that you give it an integer. Arguments can be made either way about what the "right" thing is, and in the end someone is going to be unhappy. — Christopher
– Christopher, Commented Jul 7, 2009 at 20:49

Paolo Bergantino · Accepted Answer · 2009-07-07 20:36:52Z

148

How about this?

>>> s = '23.45678'
>>> int(float(s))
23

Or...

>>> int(Decimal(s))
23

Or...

>>> int(s.split('.')[0])
23

I doubt it's going to get much simpler than that, I'm afraid. Just accept it and move on.

answered Jul 7, 2009 at 20:36

Paolo Bergantino

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3 Comments

teewuane Over a year ago

Remember to import decimal then use it as decimal.Decimal(5) or do from decimal import Decimal and use it as Decimal(5). I always forget.

Rapnar Over a year ago

You should note the type of rounding each option offers to the value.

julaine Over a year ago

Note that the s.split('.')-option will not reject and explain bad input-strings as well as the others do. You might get poor error-messages in the best case and questionable results in the worst case.

Dan Lorenc · Accepted Answer · 2009-07-07 20:41:44Z

16

What sort of rounding behavior do you want? Do you 2.67 to turn into 3, or 2. If you want to use rounding, try this:

s = '234.67'
i = int(round(float(s)))

Otherwise, just do:

s = '234.67'
i = int(float(s))

answered Jul 7, 2009 at 20:41

Dan Lorenc

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Comments

Kevin Little · Accepted Answer · 2009-07-07 20:47:25Z

4

>>> s = '23.45678'
>>> int(float(s))
23
>>> int(round(float(s)))
23
>>> s = '23.54678'
>>> int(float(s))
23
>>> int(round(float(s)))
24

You don't specify if you want rounding or not...

answered Jul 7, 2009 at 20:47

Kevin Little

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Comments

Rostyslav Dzinko · Accepted Answer · 2012-08-30 12:26:41Z

4

You could use:

s = '23.245678'
i = int(float(s))

edited Aug 30, 2012 at 12:26

Rostyslav Dzinko

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answered Jul 7, 2009 at 20:40

gbc

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Comments

JosefAssad · Accepted Answer · 2009-07-07 20:45:05Z

2

"Convert" only makes sense when you change from one data type to another without loss of fidelity. The number represented by the string is a float and will lose precision upon being forced into an int.

You want to round instead, probably (I hope that the numbers don't represent currency because then rounding gets a whole lot more complicated).

round(float('23.45678'))

answered Jul 7, 2009 at 20:45

JosefAssad

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Comments

Kathy Van Stone · Accepted Answer · 2009-07-07 20:48:21Z

1

The expression int(float(s)) mentioned by others is the best if you want to truncate the value. If you want rounding, using int(round(float(s)) if the round algorithm matches what you want (see the round documentation), otherwise you should use Decimal and one if its rounding algorithms.

answered Jul 7, 2009 at 20:48

Kathy Van Stone

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Comments

rledley · Accepted Answer · 2009-07-07 20:47:26Z

0

round(float("123.789"))

will give you an integer value, but a float type. With Python's duck typing, however, the actual type is usually not very relevant. This will also round the value, which you might not want. Replace 'round' with 'int' and you'll have it just truncated and an actual int. Like this:

int(float("123.789"))

But, again, actual 'type' is usually not that important.

answered Jul 7, 2009 at 20:47

rledley

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Comments

Ray Lutz · Accepted Answer · 2021-11-07 17:46:32Z

I believe this is a useless bug that should be corrected in Python.

int('2') --> 2 That converts the string '2' into an the integer 2.

int(2.7) --> 2 Converts a float to an int.

int('2.7') SHOULD convert to 2. This is how Perl works, for example. Yes, this does two things at once. It converts the string and when it finds it is in a representation that is a float, it should convert to int.

Otherwise, why insist that float('2') should work? It is an integer string, because there is no decimal point. So it has to convert from string which is an integer, directly to float.

I don't know but perhaps someone can answer whether the python interpreter, if the required int(float(x)) is used, if it actually goes through the process of first converting to float and then converting to int. That would make this bug even more critical to correct.

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