# Data Structures Tutorial¶

This page gives you a quick introduction to the most common use cases and default behaviour of xlwings when reading and writing values. For an in-depth documentation of how to control things using the options method, have a look at Converters.

## Single Cells¶

Single cells are by default returned either as float, unicode, None or datetime objects, depending on whether the cell contains a number, a string, is empty or represents a date:

>>> from xlwings import Workbook, Range
>>> from datetime import datetime
>>> wb = Workbook()
>>> Range('A1').value = 1
>>> Range('A1').value
1.0
>>> Range('A2').value = 'Hello'
>>> Range('A2').value
'Hello'
>>> Range('A3').value is None
True
>>> Range('A4').value = datetime(2000, 1, 1)
>>> Range('A4').value
datetime.datetime(2000, 1, 1, 0, 0)


## Lists¶

• 1d lists: Ranges that represent rows or columns in Excel are returned as simple lists, which means that once they are in Python, you’ve lost the information about the orientation. If that is an issue, read under the next point how this information can be preserved:

>>> wb = Workbook()
>>> Range('A1').value = [,,,,]  # Column orientation (nested list)
>>> Range('A1:A5').value
[1.0, 2.0, 3.0, 4.0, 5.0]
>>> Range('A1').value = [1, 2, 3, 4, 5]
>>> Range('A1:E1').value
[1.0, 2.0, 3.0, 4.0, 5.0]


To force a single cell to arrive as list, use:

>>> Range('A1').options(ndim=1).value
[1.0]


Note

To write a list in column orientation to Excel, use transpose: Range('A1').options(transpose=True).value = [1,2,3,4]

• 2d lists: If the row or column orientation has to be preserved, set ndim in the Range options. This will return the Ranges as nested lists (“2d lists”):

>>> Range('A1:A5').options(ndim=2).value
[[1.0], [2.0], [3.0], [4.0], [5.0]]
>>> Range('A1:E1').options(ndim=2).value
[[1.0, 2.0, 3.0, 4.0, 5.0]]

• 2 dimensional Ranges are automatically returned as nested lists. When assigning (nested) lists to a Range in Excel, it’s enough to just specify the top left cell as target address. This sample also makes use of index notation to read the values back into Python:

>>> Range('A10').value = [['Foo 1', 'Foo 2', 'Foo 3'], [10, 20, 30]]
>>> Range((10,1),(11,3)).value
[['Foo 1', 'Foo 2', 'Foo 3'], [10.0, 20.0, 30.0]]


Note

Try to minimize the number of interactions with Excel. It is always more efficient to do Range('A1').value = [[1,2],[3,4]] than Range('A1').value = [1, 2] and Range('A2').value = [3, 4].

## Range expanding: “table”, “vertical” and “horizontal”¶

You can get the dimensions of Excel Ranges dynamically through either the Range properties table, vertical and horizontal or through options(expand='table') (same for 'vertical' and 'horizontal'). While properties give back a changed Range object, options are only evaluated when accessing the values of a Range. The difference is best explained with an example:

>>> wb = Workbook()
>>> Range('A1').value = [[1,2], [3,4]]
>>> rng1 = Range('A1').table
>>> rng2 = Range('A1').options(expand='table')
>>> rng1.value
[[1.0, 2.0], [3.0, 4.0]]
>>> rng2.value
[[1.0, 2.0], [3.0, 4.0]]
>>> Range('A3').value = [5, 6]
>>> rng1.value
[[1.0, 2.0], [3.0, 4.0]]
>>> rng2.value
[[1.0, 2.0], [3.0, 4.0], [5.0, 6.0]]


Note

Using table together with a named Range as top left cell gives you a flexible setup in Excel: You can move around the table and change it’s size without having to adjust your code, e.g. by using something like Range('NamedRange').table.value.

## NumPy arrays¶

NumPy arrays work similar to nested lists. However, empty cells are represented by nan instead of None. If you want to read in a Range as array, set convert=np.array:

>>> import numpy as np
>>> wb = Workbook()
>>> Range('A1').value = np.eye(3)
>>> Range('A1').options(np.array, expand='table').value
array([[ 1.,  0.,  0.],
[ 0.,  1.,  0.],
[ 0.,  0.,  1.]])


## Pandas DataFrames¶

>>> wb = Workbook()
>>> df = pd.DataFrame([[1.1, 2.2], [3.3, None]], columns=['one', 'two'])
>>> df
one  two
0  1.1  2.2
1  3.3  NaN
>>> Range('A1').value = df
>>> Range('A1:C3').options(pd.DataFrame).value
one  two
0  1.1  2.2
1  3.3  NaN
# options: work for reading and writing
>>> Range('A5').options(index=False).value = df
>>> Range('A9').options(index=False, header=False).value = df


## Pandas Series¶

>>> import pandas as pd
>>> import numpy as np
>>> wb = Workbook()
>>> s = pd.Series([1.1, 3.3, 5., np.nan, 6., 8.], name='myseries')
>>> s
0    1.1
1    3.3
2    5.0
3    NaN
4    6.0
5    8.0
Name: myseries, dtype: float64
>>> Range('A1').value = s
>>> Range('A1:B7').options(pd.Series).value
0    1.1
1    3.3
2    5.0
3    NaN
4    6.0
5    8.0
Name: myseries, dtype: float64


Note

You only need to specify the top left cell when writing a list, an NumPy array or a Pandas DataFrame to Excel, e.g.: Range('A1').value = np.eye(10)