# How do I parse a string to a float or int?

## Question:

• How can I convert a `str` to `float`?
``````"545.2222"  →  545.2222
``````
• How can I convert a `str` to `int`?
``````"31"        →  31
``````

For the reverse, see Convert integer to string in Python and Converting a float to a string without rounding it.

Please instead use How can I read inputs as numbers? to close duplicate questions where OP received a string from user input and immediately wants to convert it, or was hoping for `input` (in 3.x) to convert the type automatically.

`float("545.2222")` and `int(float("545.2222"))`

``````>>> a = "545.2222"
>>> float(a)
545.22220000000004
>>> int(float(a))
545
``````

Users codelogic and harley are correct, but keep in mind if you know the string is an integer (for example, 545) you can call int(“545”) without first casting to float.

If your strings are in a list, you could use the map function as well.

``````>>> x = ["545.0", "545.6", "999.2"]
>>> map(float, x)
[545.0, 545.60000000000002, 999.20000000000005]
>>>
``````

It is only good if they’re all the same type.

Here’s another interpretation of your question (hint: it’s vague). It’s possible you’re looking for something like this:

``````def parseIntOrFloat( aString ):
return eval( aString )
``````

It works like this…

``````>>> parseIntOrFloat("545.2222")
545.22220000000004
>>> parseIntOrFloat("545")
545
``````

Theoretically, there’s an injection vulnerability. The string could, for example be `"import os; os.abort()"`. Without any background on where the string comes from, however, the possibility is theoretical speculation. Since the question is vague, it’s not at all clear if this vulnerability actually exists or not.

``````def num(s):
try:
return int(s)
except ValueError:
return float(s)
``````
``````float(x) if '.' in x else int(x)
``````

You need to take into account rounding to do this properly.

i.e. – `int(5.1)` => 5
`int(5.6)` => 5 — wrong, should be 6 so we do `int(5.6 + 0.5)` => 6

``````def convert(n):
try:
return int(n)
except ValueError:
return float(n + 0.5)
``````

The question seems a little bit old. But let me suggest a function, parseStr, which makes something similar, that is, returns integer or float and if a given ASCII string cannot be converted to none of them it returns it untouched. The code of course might be adjusted to do only what you want:

``````   >>> import string
>>> parseStr = lambda x: x.isalpha() and x or x.isdigit() and
...                      int(x) or x.isalnum() and x or
...                      len(set(string.punctuation).intersection(x)) == 1 and
...                      x.count('.') == 1 and float(x) or x
>>> parseStr('123')
123
>>> parseStr('123.3')
123.3
>>> parseStr('3HC1')
'3HC1'
>>> parseStr('12.e5')
1200000.0
>>> parseStr('12\$5')
'12\$5'
>>> parseStr('12.2.2')
'12.2.2'
``````

This is another method which deserves to be mentioned here, ast.literal_eval:

This can be used for safely evaluating strings containing Python expressions from untrusted sources without the need to parse the values oneself.

That is, a safe ‘eval’

``````>>> import ast
>>> ast.literal_eval("545.2222")
545.2222
>>> ast.literal_eval("31")
31
``````

The YAML parser can help you figure out what datatype your string is. Use `yaml.load()`, and then you can use `type(result)` to test for type:

``````>>> import yaml

>>> a = "545.2222"
>>> result = yaml.load(a)
>>> result
545.22220000000004
>>> type(result)
<type 'float'>

>>> b = "31"
>>> result = yaml.load(b)
>>> result
31
>>> type(result)
<type 'int'>

>>> c = "HI"
>>> result = yaml.load(c)
>>> result
'HI'
>>> type(result)
<type 'str'>
``````

## Localization and commas

You should consider the possibility of commas in the string representation of a number, for cases like `float("545,545.2222")` which throws an exception. Instead, use methods in `locale` to convert the strings to numbers and interpret commas correctly. The `locale.atof` method converts to a float in one step once the locale has been set for the desired number convention.

Example 1 — United States number conventions

In the United States and the UK, commas can be used as a thousands separator. In this example with American locale, the comma is handled properly as a separator:

``````>>> import locale
>>> a = u'545,545.2222'
>>> locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
'en_US.UTF-8'
>>> locale.atof(a)
545545.2222
>>> int(locale.atof(a))
545545
>>>
``````

Example 2 — European number conventions

In the majority of countries of the world, commas are used for decimal marks instead of periods. In this example with French locale, the comma is correctly handled as a decimal mark:

``````>>> import locale
>>> b = u'545,2222'
>>> locale.setlocale(locale.LC_ALL, 'fr_FR')
'fr_FR'
>>> locale.atof(b)
545.2222
``````

The method `locale.atoi` is also available, but the argument should be an integer.

## Python2 method to check if a string is a float:

``````def is_float(value):
if value is None:
return False
try:
float(value)
return True
except:
return False
``````

For the Python3 version of is_float see: Checking if a string can be converted to float in Python

A longer and more accurate name for this function could be: `is_convertible_to_float(value)`

## What is, and is not a float in Python may surprise you:

The below unit tests were done using python2. Check it that Python3 has different behavior for what strings are convertable to float. One confounding difference is that any number of interior underscores are now allowed: `(float("1_3.4") == float(13.4))` is True

``````val                   is_float(val) Note
--------------------  ----------   --------------------------------
""                    False        Blank string
"127"                 True         Passed string
True                  True         Pure sweet Truth
"True"                False        Vile contemptible lie
False                 True         So false it becomes true
"123.456"             True         Decimal
"      -127    "      True         Spaces trimmed
"tn12rn"          True         whitespace ignored
"NaN"                 True         Not a number
"NaNanananaBATMAN"    False        I am Batman
"-iNF"                True         Negative infinity
"123.E4"              True         Exponential notation
".1"                  True         mantissa only
"1_2_3.4"             False        Underscores not allowed
"12 34"               False        Spaces not allowed on interior
"1,234"               False        Commas gtfo
u'x30'               True         Unicode is fine.
"NULL"                False        Null is not special
"6e7777777777777"     True         Shrunk to infinity
"1.797693e+308"       True         This is max value
"infinity"            True         Same as inf
"infinityandBEYOND"   False        Extra characters wreck it
"12.34.56"            False        Only one dot allowed
u'四'                 False        Japanese '4' is not a float.
"#56"                 False        Pound sign
"56%"                 False        Percent of what?
"0E0"                 True         Exponential, move dot 0 places
0**0                  True         0___0  Exponentiation
"-5e-5"               True         Raise to a negative number
"+1e1"                True         Plus is OK with exponent
"+1e1^5"              False        Fancy exponent not interpreted
"+1e1.3"              False        No decimals in exponent
"-+1"                 False        Make up your mind
"(1)"                 False        Parenthesis is bad
``````

You think you know what numbers are? You are not so good as you think! Not big surprise.

## Don’t use this code on life-critical software!

Catching broad exceptions this way, killing canaries and gobbling the exception creates a tiny chance that a valid float as string will return false. The `float(...)` line of code can failed for any of a thousand reasons that have nothing to do with the contents of the string. But if you’re writing life-critical software in a duck-typing prototype language like Python, then you’ve got much larger problems.

If you aren’t averse to third-party modules, you could check out the fastnumbers module. It provides a function called fast_real that does exactly what this question is asking for and does it faster than a pure-Python implementation:

``````>>> from fastnumbers import fast_real
>>> fast_real("545.2222")
545.2222
>>> type(fast_real("545.2222"))
float
>>> fast_real("31")
31
>>> type(fast_real("31"))
int
``````

In Python, how can I parse a numeric string like “545.2222” to its corresponding float value, 542.2222? Or parse the string “31” to an integer, 31?
I just want to know how to parse a float string to a float, and (separately) an int string to an int.

It’s good that you ask to do these separately. If you’re mixing them, you may be setting yourself up for problems later. The simple answer is:

`"545.2222"` to float:

``````>>> float("545.2222")
545.2222
``````

`"31"` to an integer:

``````>>> int("31")
31
``````

# Other conversions, ints to and from strings and literals:

Conversions from various bases, and you should know the base in advance (10 is the default). Note you can prefix them with what Python expects for its literals (see below) or remove the prefix:

``````>>> int("0b11111", 2)
31
>>> int("11111", 2)
31
>>> int('0o37', 8)
31
>>> int('37', 8)
31
>>> int('0x1f', 16)
31
>>> int('1f', 16)
31
``````

If you don’t know the base in advance, but you do know they will have the correct prefix, Python can infer this for you if you pass `0` as the base:

``````>>> int("0b11111", 0)
31
>>> int('0o37', 0)
31
>>> int('0x1f', 0)
31
``````

### Non-Decimal (i.e. Integer) Literals from other Bases

If your motivation is to have your own code clearly represent hard-coded specific values, however, you may not need to convert from the bases – you can let Python do it for you automatically with the correct syntax.

You can use the apropos prefixes to get automatic conversion to integers with the following literals. These are valid for Python 2 and 3:

Binary, prefix `0b`

``````>>> 0b11111
31
``````

Octal, prefix `0o`

``````>>> 0o37
31
``````

Hexadecimal, prefix `0x`

``````>>> 0x1f
31
``````

This can be useful when describing binary flags, file permissions in code, or hex values for colors – for example, note no quotes:

``````>>> 0b10101 # binary flags
21
>>> 0o755 # read, write, execute perms for owner, read & ex for group & others
493
>>> 0xffffff # the color, white, max values for red, green, and blue
16777215
``````

### Making ambiguous Python 2 octals compatible with Python 3

If you see an integer that starts with a 0, in Python 2, this is (deprecated) octal syntax.

``````>>> 037
31
``````

It is bad because it looks like the value should be `37`. So in Python 3, it now raises a `SyntaxError`:

``````>>> 037
File "<stdin>", line 1
037
^
SyntaxError: invalid token
``````

Convert your Python 2 octals to octals that work in both 2 and 3 with the `0o` prefix:

``````>>> 0o37
31
``````
``````def get_int_or_float(v):
number_as_float = float(v)
number_as_int = int(number_as_float)
return number_as_int if number_as_float == number_as_int else number_as_float
``````
``````def num(s):
"""num(s)
num(3),num(3.7)-->3
num('3')-->3, num('3.7')-->3.7
num('3,700')-->ValueError
num('3a'),num('a3'),-->ValueError
num('3e4') --> 30000.0
"""
try:
return int(s)
except ValueError:
try:
return float(s)
except ValueError:
raise ValueError('argument is not a string of number')
``````

Use:

``````>>> str_float = "545.2222"
>>> float(str_float)
545.2222
>>> type(_) # Check its type
<type 'float'>

>>> str_int = "31"
>>> int(str_int)
31
>>> type(_) # Check its type
<type 'int'>
``````

Use:

``````def num(s):
try:
for each in s:
yield int(each)
except ValueError:
yield float(each)
a = num(["123.55","345","44"])
print a.next()
print a.next()
``````

This is the most Pythonic way I could come up with.

This is a corrected version of Totoro’s answer.

This will try to parse a string and return either `int` or `float` depending on what the string represents. It might rise parsing exceptions or have some unexpected behaviour.

``````  def get_int_or_float(v):
number_as_float = float(v)
number_as_int = int(number_as_float)
return number_as_int if number_as_float == number_as_int else
number_as_float
``````

I use this function for that

``````import ast

def parse_str(s):
try:
return ast.literal_eval(str(s))
except:
return
``````

It will convert the string to its type

``````value = parse_str('1')  # Returns Integer
value = parse_str('1.5')  # Returns Float
``````

There is also regex, because sometimes string must be prepared and normalized before casting to a number:

``````import re

def parseNumber(value, as_int=False):
try:
number = float(re.sub('[^.-d]', '', value))
if as_int:
return int(number + 0.5)
else:
return number
except ValueError:
return float('nan')  # or None if you wish
``````

Usage:

``````parseNumber('13,345')
> 13345.0

parseNumber('- 123 000')
> -123000.0

parseNumber('99999n')
> 99999.0
``````

And by the way, something to verify you have a number:

``````import numbers
def is_number(value):
return isinstance(value, numbers.Number)
# Will work with int, float, long, Decimal
``````

To `typecast` in Python use the constructor functions of the type, passing the string (or whatever value you are trying to cast) as a parameter.

For example:

``````>>>float("23.333")
23.333
``````

Behind the scenes, Python is calling the objects `__float__` method, which should return a float representation of the parameter. This is especially powerful, as you can define your own types (using classes) with a `__float__` method so that it can be casted into a float using `float(myobject)`.

This is a function which will convert any `object` (not just `str`) to `int` or `float`, based on if the actual string supplied looks like `int` or `float`. Further if it’s an object which has both `__float` and `__int__` methods, it defaults to using `__float__`

``````def conv_to_num(x, num_type='asis'):
'''Converts an object to a number if possible.
num_type: int, float, 'asis'
Defaults to floating point in case of ambiguity.
'''
import numbers

is_num, is_str, is_other = [False]*3

if isinstance(x, numbers.Number):
is_num = True
elif isinstance(x, str):
is_str = True

is_other = not any([is_num, is_str])

if is_num:
res = x
elif is_str:
is_float, is_int, is_char = [False]*3
try:
res = float(x)
if '.' in x:
is_float = True
else:
is_int = True
except ValueError:
res = x
is_char = True

else:
if num_type == 'asis':
funcs = [int, float]
else:
funcs = [num_type]

for func in funcs:
try:
res = func(x)
break
except TypeError:
continue
else:
res = x
``````

Handles hex, octal, binary, decimal, and float

This solution will handle all of the string conventions for numbers (all that I know about).

``````def to_number(n):
''' Convert any number representation to a number
This covers: float, decimal, hex, and octal numbers.
'''

try:
return int(str(n), 0)
except:
try:
# Python 3 doesn't accept "010" as a valid octal.  You must use the
# '0o' prefix
return int('0o' + n, 0)
except:
return float(n)
``````

This test case output illustrates what I’m talking about.

``````======================== CAPTURED OUTPUT =========================
to_number(3735928559)   = 3735928559 == 3735928559
to_number("0xFEEDFACE") = 4277009102 == 4277009102
to_number("0x0")        =          0 ==          0
to_number(100)          =        100 ==        100
to_number("42")         =         42 ==         42
to_number(8)            =          8 ==          8
to_number("0o20")       =         16 ==         16
to_number("020")        =         16 ==         16
to_number(3.14)         =       3.14 ==       3.14
to_number("2.72")       =       2.72 ==       2.72
to_number("1e3")        =     1000.0 ==       1000
to_number(0.001)        =      0.001 ==      0.001
to_number("0xA")        =         10 ==         10
to_number("012")        =         10 ==         10
to_number("0o12")       =         10 ==         10
to_number("0b01010")    =         10 ==         10
to_number("10")         =         10 ==         10
to_number("10.0")       =       10.0 ==         10
to_number("1e1")        =       10.0 ==         10
``````

Here is the test:

``````class test_to_number(unittest.TestCase):

def test_hex(self):
# All of the following should be converted to an integer
#
values = [

#          HEX
# ----------------------
# Input     |   Expected
# ----------------------
(0xDEADBEEF  , 3735928559), # Hex
("0xFEEDFACE", 4277009102), # Hex
("0x0"       ,          0), # Hex

#        Decimals
# ----------------------
# Input     |   Expected
# ----------------------
(100         ,        100), # Decimal
("42"        ,         42), # Decimal
]

values += [
#        Octals
# ----------------------
# Input     |   Expected
# ----------------------
(0o10        ,          8), # Octal
("0o20"      ,         16), # Octal
("020"       ,         16), # Octal
]

values += [
#        Floats
# ----------------------
# Input     |   Expected
# ----------------------
(3.14        ,       3.14), # Float
("2.72"      ,       2.72), # Float
("1e3"       ,       1000), # Float
(1e-3        ,      0.001), # Float
]

values += [
#        All ints
# ----------------------
# Input     |   Expected
# ----------------------
("0xA"       ,         10),
("012"       ,         10),
("0o12"      ,         10),
("0b01010"   ,         10),
("10"        ,         10),
("10.0"      ,         10),
("1e1"       ,         10),
]

for _input, expected in values:
value = to_number(_input)

if isinstance(_input, str):
cmd = 'to_number("{}")'.format(_input)
else:
cmd = 'to_number({})'.format(_input)

print("{:23} = {:10} == {:10}".format(cmd, value, expected))
self.assertEqual(value, expected)
``````

Pass your string to this function:

``````def string_to_number(str):
if("." in str):
try:
res = float(str)
except:
res = str
elif(str.isdigit()):
res = int(str)
else:
res = str
return(res)
``````

It will return int, float or string depending on what was passed.

### String that is an int

``````print(type(string_to_number("124")))
<class 'int'>
``````

### String that is a float

``````print(type(string_to_number("12.4")))
<class 'float'>
``````

### String that is a string

``````print(type(string_to_number("hello")))
<class 'str'>
``````

### String that looks like a float

``````print(type(string_to_number("hel.lo")))
<class 'str'>
``````

By using int and float methods we can convert a string to integer and floats.

``````s="45.8"
print(float(s))

y='67'
print(int(y))
``````

For numbers and characters together:

``````string_for_int = "498 results should get"
string_for_float = "498.45645765 results should get"
``````

First import re:

`````` import re

# For getting the integer part:
print(int(re.search(r'd+', string_for_int).group())) #498

# For getting the float part:
print(float(re.search(r'd+.d+', string_for_float).group())) #498.45645765
``````

For easy model:

``````value1 = "10"
value2 = "10.2"
print(int(value1)) # 10
print(float(value2)) # 10.2
``````
``````a = int(float(a)) if int(float(a)) == float(a) else float(a)
``````

If you are dealing with mixed integers and floats and want a consistent way to deal with your mixed data, here is my solution with the proper docstring:

``````def parse_num(candidate):
"""Parse string to number if possible
It work equally well with negative and positive numbers, integers and floats.

Args:
candidate (str): string to convert

Returns:
float | int | None: float or int if possible otherwise None
"""
try:
float_value = float(candidate)
except ValueError:
return None

# Optional part if you prefer int to float when decimal part is 0
if float_value.is_integer():
return int(float_value)
# end of the optional part

return float_value

# Test
candidates = ['34.77', '-13', 'jh', '8990', '76_3234_54']
res_list = list(map(parse_num, candidates))
print('Before:')
print(candidates)
print('After:')
print(res_list)
``````

Output:

``````Before:
['34.77', '-13', 'jh', '8990', '76_3234_54']

After:
[34.77, -13, None, 8990, 76323454]
``````

You could use `json.loads`:

``````>>> import json
123.456
>>> type(_)
<class 'float'>
>>>
``````

As you can see it becomes a type of `float`.

If you don’t want to use third party modules the following might be the most robust solution:

``````def string_to_int_or_float(s):
try:
f = float(s) # replace s with str(s) if you are not sure that s is a string
except ValueError:
print("Provided string '" + s + "' is not interpretable as a literal number.")
raise
try:
i = int(str(f).rstrip('0').rstrip('.'))
except:
return f
return i
``````

It might not be the fastest, but it handles correctly literal numbers where many other solutions fail, such as:

``````>>> string_to_int_or_float('789.')
789
>>> string_to_int_or_float('789.0')
789
>>> string_to_int_or_float('12.3e2')
1230
>>> string_to_int_or_float('12.3e-2')
0.123
>>> string_to_int_or_float('4560e-1')
456
>>> string_to_int_or_float('4560e-2')
45.6
``````

You can simply do this by

``````s = '542.22'

f = float(s) # This converts string data to float data with a decimal point
print(f)

i = int(f) # This converts string data to integer data by just taking the whole number part of it
print(i)
``````

For more information on parsing of data types check on python documentation!

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