如何使用ConfigPars中已定义的变量

Question

我在Python中使用ConfigParser

config.ini是

[general]
name: my_name
base_dir: /home/myhome/exp

exe_dir: ${base_dir}/bin

我希望exp_dir变成/home/myhome/exp/bin而不是${base_dir}/bin。

这意味着${base_dir}将被替换为/home/myhome/exp automatically。

Answer 1

可以使用ConfigParser插值

On top of the core functionality, SafeConfigParser supports interpolation. This means values can contain format strings which refer to other values in the same section, or values in a special DEFAULT section. Additional defaults can be provided on initialization.

For example:

[My Section] 
foodir: %(dir)s/whatever 
dir=frob 
long: this value continues    
    in the next line 

would resolve the %(dir)s to the value of dir (frob in this case). All reference expansions are done on demand.

你的例子变成：

[general]
name: my_name
base_dir: /home/myhome/exp

exe_dir: %(base_dir)s/bin

Answer 2

写“%（foo）s”，而不是“${foo}”。（参见http://docs.python.org/library/configparser.html并搜索“插值”。这适用于普通的ConfigParser或SafeConfigParser。）

Answer 3

在Python 3中，您可以使用${base_dir}/bin，而extended interpolation允许您使用来自其他部分的变量。示例：

[Common]
home_dir: /Users
library_dir: /Library
system_dir: /System
macports_dir: /opt/local

[Frameworks]
Python: 3.2
path: ${Common:system_dir}/Library/Frameworks/

[Arthur]
nickname: Two Sheds
last_name: Jackson
my_dir: ${Common:home_dir}/twosheds
my_pictures: ${my_dir}/Pictures
python_dir: ${Frameworks:path}/Python/Versions/${Frameworks:Python}