text: import numpy as np
  
  import pandas as pd
  from pandas import DataFrame
  import pandas.util.testing as tm
  
  import pandas.io.formats.format as fmt
  
  
  class TestEngFormatter:
      def test_eng_float_formatter(self):
          df = DataFrame({"A": [1.41, 141.0, 14100, 1410000.0]})
  
          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"
          )
          assert result == expected
  
          fmt.set_eng_float_format(use_eng_prefix=True)
          result = df.to_string()
          expected = "         A\n0    1.410\n1  141.000\n2  14.100k\n3   1.410M"
          assert result == expected
  
          fmt.set_eng_float_format(accuracy=0)
          result = df.to_string()
          expected = "         A\n0    1E+00\n1  141E+00\n2   14E+03\n3    1E+06"
          assert result == expected
  
          tm.reset_display_options()
  
      def compare(self, formatter, input, output):
          formatted_input = formatter(input)
          assert formatted_input == output
  
      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)
          assert result == " 0.000"
  
      def test_nan(self):
          # Issue #11981
  
          formatter = fmt.EngFormatter(accuracy=1, use_eng_prefix=True)
          result = formatter(np.nan)
          assert result == "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()
          assert "NaN" in result
          tm.reset_display_options()
  
      def test_inf(self):
          # Issue #11981
  
          formatter = fmt.EngFormatter(accuracy=1, use_eng_prefix=True)
          result = formatter(np.inf)
          assert result == "inf"
  