python - Python、文字列を Int または Float に変換する必要があるかどうかを判断する

Question

文字列を可能な限り厳密なデータ型である int または float に変換したいと考えています。

私は2つの文字列を持っています:

value1="0.80"     #this needs to be a float
value2="1.00"     #this needs to be an integer.

Python で value1 を Float にする必要があり、value2 を Integer にする必要があると判断するにはどうすればよいですか?

Answer 1

Pythonfloatオブジェクトにはis_integerメソッドがあります:

from ast import literal_eval
def parses_to_integer(s):
    val = literal_eval(s)
    return isinstance(val, int) or (isinstance(val, float) and val.is_integer())

Answer 2

2 つの XML 文書の違いを判別しようとしたときに、'1.0' が '1' に変換されるようにする必要がありました。だから私は私を助けるためにこの関数を書きました。また、問題の文字列リテラルが「True」または「False」の場合、他のソリューションのいくつかは失敗すると思います。いずれにせよ、この機能は私にとって非常にうまく機能します。それがあなたにも役立つことを願っています。

from ast import literal_eval

def convertString(s):
    '''
    This function will try to convert a string literal to a number or a bool
    such that '1.0' and '1' will both return 1.

    The point of this is to 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 to text files
    then do a diff.  In this case you would want <blah value='1.0'/> to match
    <blah value='1'/>.

    The solution for me is to convert the 1.0 to 1 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 if and 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

この関数の単体テストの出力は次のようになります。

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(<function B at 0x7fd9e2f27ed8>)=<function B at 0x7fd9e2f27ed8>; we expect <function B at 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 True

単体テスト コードは次のとおりです。

import unittest

# just  class for testing that the class gets returned unmolested.
#
class A: pass

# Just a function
#
def B(): pass

class Test(unittest.TestCase):


    def setUp(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      ),
        ]


    def testName(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()

Answer 3

これを行う別の方法は、次のように正規表現を使用することです。

import re
def parse_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.
    """
    if not isinstance(num, str): # optional - check type
        raise TypeError('num should be a str. Got {}.'.format(type(num)))
    if re.compile('^\s*\d+\s*$').search(num):
        return int(num)
    if re.compile('^\s*(\d*\.\d+)|(\d+\.\d*)\s*$').search(num):
        return float(num)
    raise ValueError('num is not a number. Got {}.'.format(num)) # optional

正規表現パターンに関する注意事項

^      beginning of string
$      end of string
\s*    none or more spaces
\d+    one or many digits
\d*    none or many digits
\.     literal dot
|      or

テスト

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'))

結果

1
999
1.2
0.3
4.0
12.34
0.5
ValueError: num is not a number. Got XYZ.