Version 0.9.1 (November 14, 2012) — pandas 3.0.0.dev0+2107.g341f1612a9 documentation (original) (raw)

This is a bug fix release from 0.9.0 and includes several new features and enhancements along with a large number of bug fixes. The new features include by-column sort order for DataFrame and Series, improved NA handling for the rank method, masking functions for DataFrame, and intraday time-series filtering for DataFrame.

New features#

• Series.sort, DataFrame.sort, and DataFrame.sort_index can now be specified in a per-column manner to support multiple sort orders (GH 928)
  In [2]: df = pd.DataFrame(np.random.randint(0, 2, (6, 3)),
  ...: columns=['A', 'B', 'C'])
  In [3]: df.sort(['A', 'B'], ascending=[1, 0])
  Out[3]:
  A B C
  3 0 1 1
  4 0 1 1
  2 0 0 1
  0 1 0 0
  1 1 0 0
  5 1 0 0
• DataFrame.rank now supports additional argument values for thena_option parameter so missing values can be assigned either the largest or the smallest rank (GH 1508, GH 2159)
  In [1]: df = pd.DataFrame(np.random.randn(6, 3), columns=['A', 'B', 'C'])
  In [2]: df.loc[2:4] = np.nan
  In [3]: df.rank()
  Out[3]:
  A B C
  0 3.0 2.0 1.0
  1 1.0 3.0 2.0
  2 NaN NaN NaN
  3 NaN NaN NaN
  4 NaN NaN NaN
  5 2.0 1.0 3.0
  In [4]: df.rank(na_option='top')
  Out[4]:
  A B C
  0 6.0 5.0 4.0
  1 4.0 6.0 5.0
  2 2.0 2.0 2.0
  3 2.0 2.0 2.0
  4 2.0 2.0 2.0
  5 5.0 4.0 6.0
  In [5]: df.rank(na_option='bottom')
  Out[5]:
  A B C
  0 3.0 2.0 1.0
  1 1.0 3.0 2.0
  2 5.0 5.0 5.0
  3 5.0 5.0 5.0
  4 5.0 5.0 5.0
  5 2.0 1.0 3.0
• DataFrame has new where and mask methods to select values according to a given boolean mask (GH 2109, GH 2151)

  DataFrame currently supports slicing via a boolean vector the same length as the DataFrame (inside the []). The returned DataFrame has the same number of columns as the original, but is sliced on its index.

  In [6]: df = pd.DataFrame(np.random.randn(5, 3), columns=['A', 'B', 'C'])

  In [7]: df
  Out[7]:
  A B C

0 0.276232 -1.087401 -0.673690
1 0.113648 -1.478427 0.524988
2 0.404705 0.577046 -1.715002
3 -1.039268 -0.370647 -1.157892
4 -1.344312 0.844885 1.075770

In [8]: df[df['A'] > 0]
Out[8]:
A B C
0 0.276232 -1.087401 -0.673690
1 0.113648 -1.478427 0.524988
2 0.404705 0.577046 -1.715002

If a DataFrame is sliced with a DataFrame based boolean condition (with the same size as the original DataFrame), then a DataFrame the same size (index and columns) as the original is returned, with elements that do not meet the boolean condition as NaN. This is accomplished via the new method DataFrame.where. In addition, where takes an optional other argument for replacement.

In [9]: df[df > 0]
Out[9]:
A B C
0 0.276232 NaN NaN
1 0.113648 NaN 0.524988
2 0.404705 0.577046 NaN
3 NaN NaN NaN
4 NaN 0.844885 1.075770

In [10]: df.where(df > 0)
Out[10]:
A B C
0 0.276232 NaN NaN
1 0.113648 NaN 0.524988
2 0.404705 0.577046 NaN
3 NaN NaN NaN
4 NaN 0.844885 1.075770

In [11]: df.where(df > 0, -df)
Out[11]:
A B C
0 0.276232 1.087401 0.673690
1 0.113648 1.478427 0.524988
2 0.404705 0.577046 1.715002
3 1.039268 0.370647 1.157892
4 1.344312 0.844885 1.075770

Furthermore, where now aligns the input boolean condition (ndarray or DataFrame), such that partial selection with setting is possible. This is analogous to partial setting via .ix (but on the contents rather than the axis labels)

In [12]: df2 = df.copy()

In [13]: df2[df2[1:4] > 0] = 3

In [14]: df2
Out[14]:
A B C
0 0.276232 -1.087401 -0.673690
1 3.000000 -1.478427 3.000000
2 3.000000 3.000000 -1.715002
3 -1.039268 -0.370647 -1.157892
4 -1.344312 0.844885 1.075770

DataFrame.mask is the inverse boolean operation of where.

In [15]: df.mask(df <= 0)
Out[15]:
A B C
0 0.276232 NaN NaN
1 0.113648 NaN 0.524988
2 0.404705 0.577046 NaN
3 NaN NaN NaN
4 NaN 0.844885 1.075770

• Enable referencing of Excel columns by their column names (GH 1936)
  In [1]: xl = pd.ExcelFile('data/test.xls')
  In [2]: xl.parse('Sheet1', index_col=0, parse_dates=True,
  parse_cols='A:D')
• Added option to disable pandas-style tick locators and formatters using series.plot(x_compat=True) or pandas.plot_params['x_compat'] = True (GH 2205)
• Existing TimeSeries methods at_time and between_time were added to DataFrame (GH 2149)
• DataFrame.dot can now accept ndarrays (GH 2042)
• DataFrame.drop now supports non-unique indexes (GH 2101)
• Panel.shift now supports negative periods (GH 2164)
• DataFrame now support unary ~ operator (GH 2110)

API changes#

• Upsampling data with a PeriodIndex will result in a higher frequency TimeSeries that spans the original time window
  In [1]: prng = pd.period_range('2012Q1', periods=2, freq='Q')
  In [2]: s = pd.Series(np.random.randn(len(prng)), prng)
  In [4]: s.resample('M')
  Out[4]:
  2012-01 -1.471992
  2012-02 NaN
  2012-03 NaN
  2012-04 -0.493593
  2012-05 NaN
  2012-06 NaN
  Freq: M, dtype: float64
• Period.end_time now returns the last nanosecond in the time interval (GH 2124, GH 2125, GH 1764)
  In [16]: p = pd.Period('2012')
  In [17]: p.end_time
  Out[17]: Timestamp('2012-12-31 23:59:59.999999999')
• File parsers no longer coerce to float or bool for columns that have custom converters specified (GH 2184)
  In [18]: import io
  In [19]: data = ('A,B,C\n'
  ....: '00001,001,5\n'
  ....: '00002,002,6')
  ....:
  In [20]: pd.read_csv(io.StringIO(data), converters={'A': lambda x: x.strip()})
  Out[20]:
  A B C

0 00001 1 5
1 00002 2 6

See the full release notes or issue tracker on GitHub for a complete list.

Contributors#

A total of 11 people contributed patches to this release. People with a “+” by their names contributed a patch for the first time.

• Brenda Moon +
• Chang She
• Jeff Reback +
• Justin C Johnson +
• K.-Michael Aye
• Martin Blais
• Tobias Brandt +
• Wes McKinney
• Wouter Overmeire
• timmie
• y-p