Formatting thousand separator for integers in a pandas dataframe

Question

I\'m trying to use \'{:,}\'.format(number) like the example below to format a number in a pandas dataframe:

# This works for floats and integers
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Answer 1

pandas (as of 0.20.1) does not allow overriding the default integer format in an easy way. It is hard coded in pandas.io.formats.format.IntArrayFormatter (the labmda function):

class IntArrayFormatter(GenericArrayFormatter):

    def _format_strings(self):
        formatter = self.formatter or (lambda x: '% d' % x)
        fmt_values = [formatter(x) for x in self.values]
        return fmt_values

I'm assuming is what you're actually asking for is how you can override the format for all integers: replace ("monkey patch") the IntArrayFormatter to print integer values with thousands separated by comma as follows:

import pandas

class _IntArrayFormatter(pandas.io.formats.format.GenericArrayFormatter):

    def _format_strings(self):
        formatter = self.formatter or (lambda x: ' {:,}'.format(x))
        fmt_values = [formatter(x) for x in self.values]
        return fmt_values

pandas.io.formats.format.IntArrayFormatter = _IntArrayFormatter

Note:

• before 0.20.0, the formatters were in pandas.formats.format.
• before 0.18.1, the formatters were in pandas.core.format.

Aside

For floats you do not need to jump through those hoops since there is a configuration option for it:

display.float_format: The callable should accept a floating point number and return a string with the desired format of the number. This is used in some places like SeriesFormatter. See core.format.EngFormatter for an example.