text: import numpy as np
  import pandas as pd
  from pandas import DataFrame
  from pandas.compat import u
  import pandas.formats.format as fmt
  from pandas.util import testing as tm
  
  
  class TestEngFormatter(tm.TestCase):
  
      def test_eng_float_formatter(self):
          df = DataFrame({'A': [1.41, 141., 14100, 1410000.]})
  
          fmt.set_eng_float_format()
          result = df.to_string()
          expected = ('             A\n'
                      '0    1.410E+00\n'
                      '1  141.000E+00\n'
                      '2   14.100E+03\n'
                      '3    1.410E+06')
          self.assertEqual(result, expected)
  
          fmt.set_eng_float_format(use_eng_prefix=True)
          result = df.to_string()
          expected = ('         A\n'
                      '0    1.410\n'
                      '1  141.000\n'
                      '2  14.100k\n'
                      '3   1.410M')
          self.assertEqual(result, expected)
  
          fmt.set_eng_float_format(accuracy=0)
          result = df.to_string()
          expected = ('         A\n'
                      '0    1E+00\n'
                      '1  141E+00\n'
                      '2   14E+03\n'
                      '3    1E+06')
          self.assertEqual(result, expected)
  
          self.reset_display_options()
  
      def compare(self, formatter, input, output):
          formatted_input = formatter(input)
          msg = ("formatting of %s results in '%s', expected '%s'" %
                 (str(input), formatted_input, output))
          self.assertEqual(formatted_input, output, msg)
  
      def compare_all(self, formatter, in_out):
          """
          Parameters:
          -----------
          formatter: EngFormatter under test
          in_out: list of tuples. Each tuple = (number, expected_formatting)
  
          It is tested if 'formatter(number) == expected_formatting'.
          *number* should be >= 0 because formatter(-number) == fmt is also
          tested. *fmt* is derived from *expected_formatting*
          """
          for input, output in in_out:
              self.compare(formatter, input, output)
              self.compare(formatter, -input, "-" + output[1:])
  
      def test_exponents_with_eng_prefix(self):
          formatter = fmt.EngFormatter(accuracy=3, use_eng_prefix=True)
          f = np.sqrt(2)
          in_out = [
              (f * 10 ** -24, " 1.414y"), (f * 10 ** -23, " 14.142y"),
              (f * 10 ** -22, " 141.421y"), (f * 10 ** -21, " 1.414z"),
              (f * 10 ** -20, " 14.142z"), (f * 10 ** -19, " 141.421z"),
              (f * 10 ** -18, " 1.414a"), (f * 10 ** -17, " 14.142a"),
              (f * 10 ** -16, " 141.421a"), (f * 10 ** -15, " 1.414f"),
              (f * 10 ** -14, " 14.142f"), (f * 10 ** -13, " 141.421f"),
              (f * 10 ** -12, " 1.414p"), (f * 10 ** -11, " 14.142p"),
              (f * 10 ** -10, " 141.421p"), (f * 10 ** -9, " 1.414n"),
              (f * 10 ** -8, " 14.142n"), (f * 10 ** -7, " 141.421n"),
              (f * 10 ** -6, " 1.414u"), (f * 10 ** -5, " 14.142u"),
              (f * 10 ** -4, " 141.421u"), (f * 10 ** -3, " 1.414m"),
              (f * 10 ** -2, " 14.142m"), (f * 10 ** -1, " 141.421m"),
              (f * 10 ** 0, " 1.414"), (f * 10 ** 1, " 14.142"),
              (f * 10 ** 2, " 141.421"), (f * 10 ** 3, " 1.414k"),
              (f * 10 ** 4, " 14.142k"), (f * 10 ** 5, " 141.421k"),
              (f * 10 ** 6, " 1.414M"), (f * 10 ** 7, " 14.142M"),
              (f * 10 ** 8, " 141.421M"), (f * 10 ** 9, " 1.414G"),
              (f * 10 ** 10, " 14.142G"), (f * 10 ** 11, " 141.421G"),
              (f * 10 ** 12, " 1.414T"), (f * 10 ** 13, " 14.142T"),
              (f * 10 ** 14, " 141.421T"), (f * 10 ** 15, " 1.414P"),
              (f * 10 ** 16, " 14.142P"), (f * 10 ** 17, " 141.421P"),
              (f * 10 ** 18, " 1.414E"), (f * 10 ** 19, " 14.142E"),
              (f * 10 ** 20, " 141.421E"), (f * 10 ** 21, " 1.414Z"),
              (f * 10 ** 22, " 14.142Z"), (f * 10 ** 23, " 141.421Z"),
              (f * 10 ** 24, " 1.414Y"), (f * 10 ** 25, " 14.142Y"),
              (f * 10 ** 26, " 141.421Y")]
          self.compare_all(formatter, in_out)
  
      def test_exponents_without_eng_prefix(self):
          formatter = fmt.EngFormatter(accuracy=4, use_eng_prefix=False)
          f = np.pi
          in_out = [
              (f * 10 ** -24, " 3.1416E-24"),
              (f * 10 ** -23, " 31.4159E-24"),
              (f * 10 ** -22, " 314.1593E-24"),
              (f * 10 ** -21, " 3.1416E-21"),
              (f * 10 ** -20, " 31.4159E-21"),
              (f * 10 ** -19, " 314.1593E-21"),
              (f * 10 ** -18, " 3.1416E-18"),
              (f * 10 ** -17, " 31.4159E-18"),
              (f * 10 ** -16, " 314.1593E-18"),
              (f * 10 ** -15, " 3.1416E-15"),
              (f * 10 ** -14, " 31.4159E-15"),
              (f * 10 ** -13, " 314.1593E-15"),
              (f * 10 ** -12, " 3.1416E-12"),
              (f * 10 ** -11, " 31.4159E-12"),
              (f * 10 ** -10, " 314.1593E-12"),
              (f * 10 ** -9, " 3.1416E-09"),
              (f * 10 ** -8, " 31.4159E-09"),
              (f * 10 ** -7, " 314.1593E-09"),
              (f * 10 ** -6, " 3.1416E-06"),
              (f * 10 ** -5, " 31.4159E-06"),
              (f * 10 ** -4, " 314.1593E-06"),
              (f * 10 ** -3, " 3.1416E-03"),
              (f * 10 ** -2, " 31.4159E-03"),
              (f * 10 ** -1, " 314.1593E-03"),
              (f * 10 ** 0, " 3.1416E+00"),
              (f * 10 ** 1, " 31.4159E+00"),
              (f * 10 ** 2, " 314.1593E+00"),
              (f * 10 ** 3, " 3.1416E+03"),
              (f * 10 ** 4, " 31.4159E+03"),
              (f * 10 ** 5, " 314.1593E+03"),
              (f * 10 ** 6, " 3.1416E+06"),
              (f * 10 ** 7, " 31.4159E+06"),
              (f * 10 ** 8, " 314.1593E+06"),
              (f * 10 ** 9, " 3.1416E+09"),
              (f * 10 ** 10, " 31.4159E+09"),
              (f * 10 ** 11, " 314.1593E+09"),
              (f * 10 ** 12, " 3.1416E+12"),
              (f * 10 ** 13, " 31.4159E+12"),
              (f * 10 ** 14, " 314.1593E+12"),
              (f * 10 ** 15, " 3.1416E+15"),
              (f * 10 ** 16, " 31.4159E+15"),
              (f * 10 ** 17, " 314.1593E+15"),
              (f * 10 ** 18, " 3.1416E+18"),
              (f * 10 ** 19, " 31.4159E+18"),
              (f * 10 ** 20, " 314.1593E+18"),
              (f * 10 ** 21, " 3.1416E+21"),
              (f * 10 ** 22, " 31.4159E+21"),
              (f * 10 ** 23, " 314.1593E+21"),
              (f * 10 ** 24, " 3.1416E+24"),
              (f * 10 ** 25, " 31.4159E+24"),
              (f * 10 ** 26, " 314.1593E+24")]
          self.compare_all(formatter, in_out)
  
      def test_rounding(self):
          formatter = fmt.EngFormatter(accuracy=3, use_eng_prefix=True)
          in_out = [(5.55555, ' 5.556'), (55.5555, ' 55.556'),
                    (555.555, ' 555.555'), (5555.55, ' 5.556k'),
                    (55555.5, ' 55.556k'), (555555, ' 555.555k')]
          self.compare_all(formatter, in_out)
  
          formatter = fmt.EngFormatter(accuracy=1, use_eng_prefix=True)
          in_out = [(5.55555, ' 5.6'), (55.5555, ' 55.6'), (555.555, ' 555.6'),
                    (5555.55, ' 5.6k'), (55555.5, ' 55.6k'), (555555, ' 555.6k')]
          self.compare_all(formatter, in_out)
  
          formatter = fmt.EngFormatter(accuracy=0, use_eng_prefix=True)
          in_out = [(5.55555, ' 6'), (55.5555, ' 56'), (555.555, ' 556'),
                    (5555.55, ' 6k'), (55555.5, ' 56k'), (555555, ' 556k')]
          self.compare_all(formatter, in_out)
  
          formatter = fmt.EngFormatter(accuracy=3, use_eng_prefix=True)
          result = formatter(0)
          self.assertEqual(result, u(' 0.000'))
  
      def test_nan(self):
          # Issue #11981
  
          formatter = fmt.EngFormatter(accuracy=1, use_eng_prefix=True)
          result = formatter(np.nan)
          self.assertEqual(result, u('NaN'))
  
          df = pd.DataFrame({'a': [1.5, 10.3, 20.5],
                             'b': [50.3, 60.67, 70.12],
                             'c': [100.2, 101.33, 120.33]})
          pt = df.pivot_table(values='a', index='b', columns='c')
          fmt.set_eng_float_format(accuracy=1)
          result = pt.to_string()
          self.assertTrue('NaN' in result)
          self.reset_display_options()
  
      def test_inf(self):
          # Issue #11981
  
          formatter = fmt.EngFormatter(accuracy=1, use_eng_prefix=True)
          result = formatter(np.inf)
          self.assertEqual(result, u('inf'))
  