Python, Determine If A String Should Be Converted Into Int Or Float
I want to convert a string to the tightest possible datatype: int or float. I have two strings: value1='0.80' #this needs to be a float value2='1.00' #this needs to be an i
Solution 1:
defisfloat(x):
try:
a = float(x)
except (TypeError, ValueError):
returnFalseelse:
returnTruedefisint(x):
try:
a = float(x)
b = int(a)
except (TypeError, ValueError):
returnFalseelse:
return a == b
Solution 2:
Python float objects have an is_integer method:
from ast import literal_eval
defparses_to_integer(s):
val = literal_eval(s)
returnisinstance(val, int) or (isinstance(val, float) and val.is_integer())
Solution 3:
defcoerce(x):
try:
a = float(x)
b = int(x)
if a != b:
return a
else:
return b
except:
raise ValueError("failed to coerce str to int or float")
Solution 4:
I had to handle the case of ensuring that '1.0' gets converted to '1' when I was trying to determine the differences between two XML documents. So I wrote this function to help me. I also think that some of the other solutions will fail when the string literal in question is 'True' or 'False'. At any rate this function works very well for me. I hope that it will help you too.
from ast import literal_eval
def convertString(s):
'''
This function will tryto convert a string literal to a number or a bool
such that '1.0' and '1' will both return 1.
The point of this isto ensure that '1.0' and '1' return as int(1) and that'False' and 'True' are returned as bools not numbers.
This is useful for generating text that may contain numbers for diff
purposes. For example you may want to dump two XML documents totext files
thendo a diff. In this case you would want <blah value='1.0'/> to match
<blah value='1'/>.
The solution formeisto convert the 1.0to1 so that diff doesn't see a
difference.
If s doesn't evaluate to a literal then s will simply be returned UNLESS the
literal is a float with no fractional part. (i.e. 1.0 will become 1)
If s evaluates to float or a float literal (i.e. '1.1') then a float will be
returned ifand only if the float has no fractional part.
if s evaluates as a valid literal then the literal will be returned. (e.g.
'1' will become 1 and 'False' will become False)'''if isinstance(s, str):
# It's a string. Does it represnt a literal?
#
try:
val = literal_eval(s)
except:
# s doesn't represnt any sort of literal so no conversion will be
# done.
#
val = s
else:
# It's already something other than a string
#
val = s
##
# Is the float actually an int? (i.e. is the float 1.0 ?)
#
if isinstance(val, float):
if val.is_integer():
return int(val)
# It really is a float
return val
return val
The output of the unit test of this function produces:
convertString("1")=1; we expect 1
convertString("1.0")=1; we expect 1
convertString("1.1")=1.1; we expect 1.1
convertString("010")=8; we expect 8
convertString("0xDEADBEEF")=3735928559; we expect 3735928559
convertString("hello")="hello"; we expect "hello"
convertString("false")="false"; we expect "false"
convertString("true")="true"; we expect "true"
convertString("False")=False; we expect False
convertString("True")=True; we expect True
convertString(sri.gui3.xmlSamples.test_convertString.A)=sri.gui3.xmlSamples.test_convertString.A; we expect sri.gui3.xmlSamples.test_convertString.A
convertString(<functionBat 0x7fd9e2f27ed8>)=<functionBat 0x7fd9e2f27ed8>; we expect <functionBat 0x7fd9e2f27ed8>
convertString(1)=1; we expect 1
convertString(1.0)=1; we expect 1
convertString(1.1)=1.1; we expect 1.1
convertString(3735928559)=3735928559; we expect 3735928559
convertString(False)=False; we expect False
convertString(True)=True; we expect TrueThe unit test code follows:
import unittest
# just class for testing that the class gets returned unmolested.#classA: pass# Just a function#defB(): passclassTest(unittest.TestCase):
defsetUp(self):
self.conversions = [
# input | expected
('1' ,1 ),
('1.0' ,1 ), # float with no fractional part
('1.1' ,1.1 ),
('010' ,8 ), # octal
('0xDEADBEEF',0xDEADBEEF), # hex
('hello' ,'hello' ),
('false' ,'false' ),
('true' ,'true' ),
('False' ,False ), # bool
('True' ,True ), # bool
(A ,A ), # class
(B ,B ), # function
(1 ,1 ),
(1.0 ,1 ), # float with no fractional part
(1.1 ,1.1 ),
(0xDEADBEEF ,0xDEADBEEF),
(False ,False ),
(True ,True ),
]
deftestName(self):
for s,expected in self.conversions:
rval = convertString(s)
print'convertString({s})={rval}; we expect {expected}'.format(**locals())
self.assertEqual(rval, expected)
if __name__ == "__main__":
#import sys;sys.argv = ['', 'Test.testName']
unittest.main()
Solution 5:
Another way to do this, is by using regex like this:
import re
defparse_str(num):
"""
Parse a string that is expected to contain a number.
:param num: str. the number in string.
:return: float or int. Parsed num.
"""ifnotisinstance(num, str): # optional - check typeraise TypeError('num should be a str. Got {}.'.format(type(num)))
if re.compile('^\s*\d+\s*$').search(num):
returnint(num)
if re.compile('^\s*(\d*\.\d+)|(\d+\.\d*)\s*$').search(num):
returnfloat(num)
raise ValueError('num is not a number. Got {}.'.format(num)) # optionalNotes on Regex Pattern
^ beginning of string
$ endof string
\s*noneor more spaces
\d+oneor many digits
\d*noneor many digits
\. literal dot
|orTest
print(parse_str('1'))
print(parse_str('999'))
print(parse_str('1.2'))
print(parse_str('.3'))
print(parse_str('4.'))
print(parse_str('12.34'))
print(parse_str(' 0.5 '))
print(parse_str('XYZ'))
Result
19991.20.34.012.340.5ValueError: num isnot a number. Got XYZ.
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