Pandas - how to coerce only empty string values in dataframe column to NaN

With data like below

colVals = [['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.703', '', '', '', '', '', '21', '', '3', '   217', '891', '18', '', '', '', '', '', '', '', '', ''], ['05:17:55.707', '', '', '', '', '', '18', '', '3', '   185', '892', '0', '', '', '', '', '', '', '', '', ''], ['05:17:55.707', '', '', '', '', '', '21', '', '3', '   185', '892', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.707', '', '', '', '', '', '17', '', '3', '    73', '892', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.707', '', '', '', '', '', '17', '', '3', '   185', '892', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.707', '', '', '', '', '', '21', '', '3', '    73', '892', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.708', '268', '4', '28', '-67.60', '13', '', '2', '', '', '', '', '2', '13.128', '', '', '', '', '', '', ''], ['05:17:55.711', '', '', '', '', '', '18', '', '3', '    57', '892', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.711', '', '', '', '', '', '21', '', '3', '   201', '892', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.711', '', '', '', '', '', '21', '', '3', '    25', '892', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.723', '', '', '', '', '', '21', '', '3', '   217', '893', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.723', '', '', '', '', '', '21', '', '3', '   217', '893', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.723', '', '', '', '', '', '21', '', '3', '   217', '893', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.726', '268', '4', '', '-67.80', '', '', '', '', '', '', '', '', '12.902', '', '', '', '', '', '', ''], ['05:17:55.728', '', '', '28', '', '12', '31', '2', '3', '   185', '894', '0', '1', '', '', '', '', '', '', '', ''], ['05:17:55.728', '', '', '', '', '', '31', '', '3', '   185', '894', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.731', '', '', '', '', '', '31', '', '3', '   217', '894', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.731', '', '', '', '', '', '20', '', '3', '   217', '894', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.731', '', '', '', '', '', '20', '', '3', '   217', '894', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.731', '', '', '', '', '', '20', '', '3', '   217', '894', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.743', '', '', '', '', '', '20', '', '3', '   217', '895', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.743', '', '', '', '', '', '20', '', '3', '   217', '895', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.743', '', '', '', '', '', '20', '', '3', '   217', '895', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.746', '268', '4', '', '-67.82', '', '', '', '', '', '', '', '', '13.243', '', '', '', '', '', '', ''], ['05:17:55.747', '', '', '28', '', '13', '20', '2', '3', '   185', '896', '1', '2', '', '', '', '', '', '', '', ''], ['05:17:55.747', '', '', '', '', '', '20', '', '3', '   185', '896', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.747', '', '', '', '', '', '30', '', '3', '   217', '896', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.751', '', '', '', '', '', '18', '', '3', '   217', '896', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.751', '', '', '', '', '', '21', '', '3', '   217', '896', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.751', '', '', '', '', '', '21', '', '3', '   217', '896', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.751', '', '', '', '', '', '21', '', '3', '   217', '896', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.763', '', '', '', '', '', '31', '', '3', '   217', '897', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.763', '', '', '', '', '', '30', '', '3', '   217', '897', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.763', '', '', '', '', '', '20', '', '3', '   217', '897', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.763', '', '', '', '', '', '20', '', '3', '   217', '897', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.766', '268', '4', '', '-67.13', '', '', '', '', '', '', '', '', '13.685', '', '', '', '', '', '', ''], ['05:17:55.768', '', '', '28', '', '12', '20', '2', '3', '   185', '898', '3', '2', '', '', '', '', '', '', '', ''], ['05:17:55.768', '', '', '', '', '', '16', '', '3', '   217', '898', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.771', '', '', '', '', '', '18', '', '3', '   217', '898', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.771', '', '', '', '', '', '20', '', '3', '   217', '898', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.771', '', '', '', '', '', '20', '', '3', '   217', '898', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '   217', '899', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '    41', '899', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '    25', '899', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '   217', '899', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '   217', '899', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '   217', '899', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.784', '', '', '', '', '', '20', '', '3', '   217', '899', '18', '', '', '', '', '', '', '', '', ''], ['05:17:55.786', '268', '4', '', '-67.66', '', '', '', '', '', '', '', '', '13.683', '', '', '', '', '', '', ''], ['05:17:55.788', '', '', '28', '', '13', '18', '2', '3', '   185', '900', '0', '2', '', '', '', '', '', '', '', ''], ['05:17:55.788', '', '', '', '', '', '20', '', '3', '   185', '900', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.788', '', '', '', '', '', '20', '', '3', '   185', '900', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.788', '', '', '', '', '', '16', '', '3', '    41', '900', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.788', '', '', '', '', '', '17', '', '3', '   185', '900', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.791', '', '', '', '', '', '20', '', '3', '   105', '900', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.791', '', '', '', '', '', '20', '', '3', '    89', '900', '8', '', '', '', '', '', '', '', '', ''], ['05:17:55.791', '', '', '', '', '', '18', '', '3', '   217', '900', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.791', '', '', '', '', '', '20', '', '3', '   217', '900', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.791', '', '', '', '', '', '20', '', '3', '    25', '900', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.806', '268', '4', '', '-67.50', '', '', '', '', '', '', '', '', '14.023', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '28', '', '12', '31', '2', '3', '   185', '902', '0', '1', '', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '', '', '', '31', '', '3', '   185', '902', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '', '', '', '20', '', '3', '    25', '902', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '', '', '', '20', '', '3', '    25', '902', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '', '', '', '16', '', '3', '   217', '902', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.808', '', '', '', '', '', '16', '', '3', '   217', '902', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '20', '', '3', '    89', '902', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '20', '', '3', '   121', '902', '8', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '18', '', '3', '   217', '902', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '20', '', '3', '   217', '902', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '20', '', '3', '    73', '902', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.811', '', '', '', '', '', '20', '', '3', '     9', '902', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '20', '', '3', '   217', '902', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '20', '', '3', '    25', '902', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '20', '', '3', '   217', '902', '18', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '18', '', '3', '   217', '903', '0', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '21', '', '3', '   217', '903', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '19', '', '3', '   105', '903', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.815', '', '', '', '', '', '21', '', '3', '    41', '903', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '   217', '903', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '     9', '903', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '   105', '903', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '   217', '903', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '   217', '903', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '   121', '903', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.823', '', '', '', '', '', '21', '', '3', '    89', '903', '18', '', '', '', '', '', '', '', '', ''], ['05:17:55.826', '268', '4', '', '-67.51', '', '', '', '', '', '', '', '', '14.370', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '28', '', '12', '18', '2', '3', '   185', '904', '0', '1', '', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '', '', '', '21', '', '3', '   185', '904', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '', '', '', '21', '', '3', '   185', '904', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '', '', '', '21', '', '3', '   185', '904', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '', '', '', '17', '', '3', '   217', '904', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.828', '', '', '', '', '', '17', '', '3', '   217', '904', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.831', '', '', '', '', '', '21', '', '3', '   217', '904', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.831', '', '', '', '', '', '20', '', '3', '   169', '904', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.831', '', '', '', '', '', '20', '', '3', '   217', '904', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.831', '', '', '', '', '', '20', '', '3', '   217', '904', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.846', '268', '4', '', '-67.01', '', '', '', '', '', '', '', '', '14.227', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '28', '', '13', '19', '2', '3', '    57', '906', '1', '2', '', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '', '', '', '19', '', '3', '    41', '906', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '', '', '', '19', '', '3', '    73', '906', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '', '', '', '16', '', '3', '   217', '906', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '', '', '', '16', '', '3', '   217', '906', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.848', '', '', '', '', '', '19', '', '3', '     9', '906', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.851', '', '', '', '', '', '20', '', '3', '   121', '906', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.851', '', '', '', '', '', '20', '', '3', '    57', '906', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.851', '', '', '', '', '', '20', '', '3', '   105', '906', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '20', '', '3', '   217', '906', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '20', '', '3', '   217', '906', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '20', '', '3', '   105', '906', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '17', '', '3', '   185', '907', '0', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '20', '', '3', '   217', '907', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.855', '', '', '', '', '', '20', '', '3', '     9', '907', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '   217', '907', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '    57', '907', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '   153', '907', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '   217', '907', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '   217', '907', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '    57', '907', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.864', '', '', '', '', '', '20', '', '3', '   105', '907', '18', '', '', '', '', '', '', '', '', ''], ['05:17:55.867', '', '', '', '', '', '17', '', '3', '   185', '908', '0', '', '', '', '', '', '', '', '', ''], ['05:17:55.867', '', '', '', '', '', '20', '', '3', '   185', '908', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.867', '', '', '', '', '', '20', '', '3', '     9', '908', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.867', '', '', '', '', '', '16', '', '3', '    73', '908', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.868', '268', '4', '28', '-66.79', '13', '', '2', '', '', '', '', '2', '13.969', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '20', '', '3', '   105', '908', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '20', '', '3', '    25', '908', '8', '', '', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '17', '', '3', '   217', '908', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '21', '', '3', '   217', '908', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '21', '', '3', '     9', '908', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.871', '', '', '', '', '', '21', '', '3', '   121', '908', '13', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '   217', '908', '15', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '   217', '908', '16', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '    57', '908', '17', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '18', '', '3', '    73', '909', '0', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '   217', '909', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '    89', '909', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.875', '', '', '', '', '', '21', '', '3', '    89', '909', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.886', '268', '4', '', '-67.48', '', '', '', '', '', '', '', '', '13.857', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '28', '', '12', '31', '2', '3', '   185', '910', '0', '1', '', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '', '', '', '21', '', '3', '    89', '910', '1', '', '', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '', '', '', '21', '', '3', '     9', '910', '2', '', '', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '', '', '', '21', '', '3', '   185', '910', '3', '', '', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '', '', '', '17', '', '3', '   217', '910', '5', '', '', '', '', '', '', '', '', ''], ['05:17:55.888', '', '', '', '', '', '17', '', '3', '   217', '910', '6', '', '', '', '', '', '', '', '', ''], ['05:17:55.891', '', '', '', '', '', '21', '', '3', '    89', '910', '7', '', '', '', '', '', '', '', '', ''], ['05:17:55.891', '', '', '', '', '', '21', '', '3', '    73', '910', '8', '', '', '', '', '', '', '', '', ''], ['05:17:55.891', '', '', '', '', '', '18', '', '3', '   217', '910', '10', '', '', '', '', '', '', '', '', ''], ['05:17:55.891', '', '', '', '', '', '21', '', '3', '   217', '910', '11', '', '', '', '', '', '', '', '', ''], ['05:17:55.891', '', '', '', '', '', '21', '', '3', '    57', '910', '12', '', '', '', '', '', '', '', '', ''], ['05:17:55.893', '', '', '', '', '', '', '', '', '', '', '', '', '', '  0', 'PSH', '-10.0', '  8', '  8', '  0', ''], ['05:17:55.893', '', '', '', '', '', '', '', '', '', '', '', '', '', ' 13', 'PCH', ' 13.0', ' 48', '  1', '  0', ''], ['05:17:55.893', '', '', '', '', '', '', '', '', '', '', '', '', '', '  0', 'PSH', '-13.0', ' 20', '  4', '  0', ''], ['05:17:55.893', '', '', '', '', '', '', '', '', '', '', '', '', '', ' 13', 'PCH', ' 17.0', ' 48', '  4', '  0', ''], ['05:17:55.893', '', '', '', '', '', '', '', '', '', '', '', '', '', '  0', 'PSH', ' -9.0', '  0', ' 12', '  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colNames = ['Time', 'Col01', 'Col02', 'Col03', 'Col04', 'Col05', 'Col06', 'Col07', 'Col08', 'Col09', 'Col10', 'Col11', 'Col12', 'Col13', 'Col14', 'Col15', 'Col16', 'Col17', 'Col18', 'Col19', 'Col20']

I'm creating a data frame

df = pd.DataFrame(colVals, columns=colNames)

This gives all the columns as object (Strings)

df.dtypes
Out[28]: 
Time     object
Col01    object
Col02    object
Col03    object
Col04    object
Col05    object
Col06    object
Col07    object
Col08    object
Col09    object
Col10    object
Col11    object
Col12    object
Col13    object
Col14    object
Col15    object
Col15    object
Col16    object
Col17    object
Col18    object
Col19    object
dtype: object

I want to convert the columns as appropiate data types as floats, int and strings. For example Col01 should be int, Col04 should be float and Col15 should be string.

using the answer here -

df = df.set_index('Time')
def func(x):
    a = pd.to_numeric(x, errors='coerce')
    try:
        return a.astype('Int64')
    except:
        return a

df1 = df.apply(func)

This works for floats and int type columns, but it also converts all strings to NaN. The desired results is that only null strings '' shall be converted to NaN. How to go about this?

from Pandas - how to coerce only empty string values in dataframe column to NaN