数据结构教程¶

This tutorial 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 the behavior using the options method, have a look at Converters and Options.

后面所有的示例代码都依赖下面的模块导入语句：

>>> import xlwings as xw

单个单元格¶

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:

>>> import datetime as dt
>>> sheet = xw.Book().sheets[0]
>>> sheet['A1'].value = 1
>>> sheet['A1'].value
1.0
>>> sheet['A2'].value = 'Hello'
>>> sheet['A2'].value
'Hello'
>>> sheet['A3'].value is None
True
>>> sheet['A4'].value = dt.datetime(2000, 1, 1)
>>> sheet['A4'].value
datetime.datetime(2000, 1, 1, 0, 0)

列表¶

一维列表：在Excel中代表行或者列的区域，在Python中返回的都是一个列表。所以一旦把他们读入Python中，就是丢失行、列的方向信息。如果这个的确是个问题的话，下面一个知识点会说明如何保留这些信息：
```
>>> sheet = xw.Book().sheets[0]
>>> sheet['A1'].value = [[1],[2],[3],[4],[5]]  # Column orientation (nested list)
>>> sheet['A1:A5'].value
[1.0, 2.0, 3.0, 4.0, 5.0]
>>> sheet['A1'].value = [1, 2, 3, 4, 5]
>>> sheet['A1:E1'].value
[1.0, 2.0, 3.0, 4.0, 5.0]
```
To force a single cell to arrive as list, use:
```
>>> sheet['A1'].options(ndim=1).value
[1.0]
```
备注

To write a list in column orientation to Excel, use transpose: sheet.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"):

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

二维区域会自动返回为嵌套列表。当把一个嵌套列表赋值给Excel区域的时候，只要明确目标区域的左上角单元格地址就行了。下面的例子也使用了索引方式把区域的值读会Python：
```
>>> sheet['A10'].value = [['Foo 1', 'Foo 2', 'Foo 3'], [10, 20, 30]]
>>> sheet.range((10,1),(11,3)).value
[['Foo 1', 'Foo 2', 'Foo 3'], [10.0, 20.0, 30.0]]
```

备注

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

区域扩展¶

You can get the dimensions of Excel Ranges dynamically through either the method expand or through the expand keyword in the options method. While expand gives back an expanded Range object, options are only evaluated when accessing the values of a Range. The difference is best explained with an example:

>>> sheet = xw.Book().sheets[0]
>>> sheet['A1'].value = [[1,2], [3,4]]
>>> range1 = sheet['A1'].expand('table')  # or just .expand()
>>> range2 = sheet['A1'].options(expand='table')
>>> range1.value
[[1.0, 2.0], [3.0, 4.0]]
>>> range2.value
[[1.0, 2.0], [3.0, 4.0]]
>>> sheet['A3'].value = [5, 6]
>>> range1.value
[[1.0, 2.0], [3.0, 4.0]]
>>> range2.value
[[1.0, 2.0], [3.0, 4.0], [5.0, 6.0]]

'table' expands to 'down' and 'right', the other available options which can be used for column or row only expansion, respectively.

备注

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

NumPy数组¶

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 in the options method:

>>> import numpy as np
>>> sheet = xw.Book().sheets[0]
>>> sheet['A1'].value = np.eye(3)
>>> sheet['A1'].options(np.array, expand='table').value
array([[ 1.,  0.,  0.],
       [ 0.,  1.,  0.],
       [ 0.,  0.,  1.]])

Pandas数据表(DataFrame)¶

>>> sheet = xw.Book().sheets[0]
>>> 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
>>> sheet['A1'].value = df
>>> sheet['A1:C3'].options(pd.DataFrame).value
   one  two
0  1.1  2.2
1  3.3  NaN
# options: work for reading and writing
>>> sheet['A5'].options(index=False).value = df
>>> sheet['A9'].options(index=False, header=False).value = df

Pandas的序列(Serie)¶

>>> import pandas as pd
>>> import numpy as np
>>> sheet = xw.Book().sheets[0]
>>> 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
>>> sheet['A1'].value = s
>>> sheet['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

备注

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

Chunking: Read/Write big DataFrames etc.¶

When you read and write from or to big ranges, you may have to chunk them or you will hit a timeout or a memory error. The ideal chunksize will depend on your system and size of the array, so you will have to try out a few different chunksizes to find one that works well:

import pandas as pd
import numpy as np
sheet = xw.Book().sheets[0]
data = np.arange(75_000 * 20).reshape(75_000, 20)
df = pd.DataFrame(data=data)
sheet['A1'].options(chunksize=10_000).value = df

And the same for reading:

# As DataFrame
df = sheet['A1'].expand().options(pd.DataFrame, chunksize=10_000).value
# As list of list
df = sheet['A1'].expand().options(chunksize=10_000).value