pandas.DataFrame.align#

DataFrame.align(other, join='outer', axis=None, level=None, copy=<no_default>, fill_value=None)[source]#

Align two objects on their axes with the specified join method.

Join method is specified for each axis Index.

Parameters:
otherDataFrame or Series

The object to align with.

join{‘outer’, ‘inner’, ‘left’, ‘right’}, default ‘outer’

Type of alignment to be performed.

  • left: use only keys from left frame, preserve key order.

  • right: use only keys from right frame, preserve key order.

  • outer: use union of keys from both frames, sort keys lexicographically.

  • inner: use intersection of keys from both frames, preserve the order of the left keys.

axisallowed axis of the other object, default None

Align on index (0), columns (1), or both (None).

levelint or level name, default None

Broadcast across a level, matching Index values on the passed MultiIndex level.

copybool, default False

This keyword is now ignored; changing its value will have no impact on the method.

Deprecated since version 3.0.0: This keyword is ignored and will be removed in pandas 4.0. Since pandas 3.0, this method always returns a new object using a lazy copy mechanism that defers copies until necessary (Copy-on-Write). See the user guide on Copy-on-Write for more details.

fill_valuescalar, default np.nan

Value to use for missing values. Defaults to NaN, but can be any “compatible” value.

Returns:
tuple of (Series/DataFrame, type of other)

Aligned objects.

See also

Series.align

Align two objects on their axes with specified join method.

DataFrame.align

Align two objects on their axes with specified join method.

Examples

>>> df = pd.DataFrame(
...     [[1, 2, 3, 4], [6, 7, 8, 9]], columns=["D", "B", "E", "A"], index=[1, 2]
... )
>>> other = pd.DataFrame(
...     [[10, 20, 30, 40], [60, 70, 80, 90], [600, 700, 800, 900]],
...     columns=["A", "B", "C", "D"],
...     index=[2, 3, 4],
... )
>>> df
   D  B  E  A
1  1  2  3  4
2  6  7  8  9
>>> other
    A    B    C    D
2   10   20   30   40
3   60   70   80   90
4  600  700  800  900

Align on columns:

>>> left, right = df.align(other, join="outer", axis=1)
>>> left
   A  B   C  D  E
1  4  2 NaN  1  3
2  9  7 NaN  6  8
>>> right
    A    B    C    D   E
2   10   20   30   40 NaN
3   60   70   80   90 NaN
4  600  700  800  900 NaN

We can also align on the index:

>>> left, right = df.align(other, join="outer", axis=0)
>>> left
    D    B    E    A
1  1.0  2.0  3.0  4.0
2  6.0  7.0  8.0  9.0
3  NaN  NaN  NaN  NaN
4  NaN  NaN  NaN  NaN
>>> right
    A      B      C      D
1    NaN    NaN    NaN    NaN
2   10.0   20.0   30.0   40.0
3   60.0   70.0   80.0   90.0
4  600.0  700.0  800.0  900.0

Finally, the default axis=None will align on both index and columns:

>>> left, right = df.align(other, join="outer", axis=None)
>>> left
     A    B   C    D    E
1  4.0  2.0 NaN  1.0  3.0
2  9.0  7.0 NaN  6.0  8.0
3  NaN  NaN NaN  NaN  NaN
4  NaN  NaN NaN  NaN  NaN
>>> right
       A      B      C      D   E
1    NaN    NaN    NaN    NaN NaN
2   10.0   20.0   30.0   40.0 NaN
3   60.0   70.0   80.0   90.0 NaN
4  600.0  700.0  800.0  900.0 NaN
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