python標准庫介紹——18 StringIO 模塊詳解

==StringIO 模塊==


[Example 2-8 #eg-2-8] 展示了 ``StringIO`` 模塊的使用. 它實現了一個工作在內存的文件對象
(內存文件). 在大多需要標准文件對象的地方都可以使用它來替換.

====Example 2-8. 使用 StringIO 模塊從內存文件讀入內容====[eg-2-8]

```
File: stringio-example-1.py

import StringIO

MESSAGE = "That man is depriving a village somewhere of a computer scientist."

file = StringIO.StringIO(MESSAGE)

print file.read()

*B*That man is depriving a village somewhere of a computer scientist.*b*
```

``StringIO`` 類實現了內建文件對象的所有方法, 此外還有 ``getvalue`` 方法用來返回它內部的字符串值. 
[Example 2-9 #eg-2-9] 展示了這個方法.

====Example 2-9. 使用 StringIO 模塊向內存文件寫入內容====[eg-2-9]

```
File: stringio-example-2.py

import StringIO

file = StringIO.StringIO()
file.write("This man is no ordinary man. ")
file.write("This is Mr. F. G. Superman.")

print file.getvalue()

*B*This man is no ordinary man. This is Mr. F. G. Superman.*b*
```

``StringIO`` 可以用於重新定向 Python 解釋器的輸出, 如 [Example 2-10 #eg-2-10] 所示.

====Example 2-10. 使用 StringIO 模塊捕獲輸出====[eg-2-10]

```
File: stringio-example-3.py

import StringIO
import string, sys

stdout = sys.stdout

sys.stdout = file = StringIO.StringIO()

print """
According to Gbaya folktales, trickery and guile
are the best ways to defeat the python, king of
snakes, which was hatched from a dragon at the
world's start. -- National Geographic, May 1997
"""

sys.stdout = stdout

print string.upper(file.getvalue())

*B*ACCORDING TO GBAYA FOLKTALES, TRICKERY AND GUILE
ARE THE BEST WAYS TO DEFEAT THE PYTHON, KING OF
SNAKES, WHICH WAS HATCHED FROM A DRAGON AT THE
WORLD'S START. -- NATIONAL GEOGRAPHIC, MAY 1997*b*
```