我想根据用户选择的值导入一些包。
默认值为file1.py：
from files import file1
如果用户选择file2，则应为：
from files import file2
号
在PHP中，我可以使用变量：
$file_name = 'file1';
include($$file_name);
$file_name = 'file2';
include($$file_name);
。
我怎样才能在python中做到这一点？
别这样！使用输入通常是不可信的，并且基于它盲目地评估代码是一个坏主意。
谢谢，我现在使用默认设置导入。
python没有直接等同于php的"变量"的特性。要获得"变量"的值(或任何其他表达式的值)，可以使用eval函数。
foo ="Hello World"
print eval("foo")
号
但是，这不能用在import语句中。
可以使用__import__函数使用变量导入。
package ="os"
name ="path"
imported = getattr(__import__(package, fromlist=[name]), name)
等于
from os import path as imported
。
旧线索，但我需要答案，所以其他人可能…
在python 2.7+中有一种更简单的方法可以做到这一点：
import importlib
my_module = importlib.import_module("package.path.%s" % module_name)
。
小贴士：你需要一个package.path.__init__.py才能导入工作。
正如Fredrik Lundh所说：
Anyway, here’s how these statements and functions work:
import X imports the module X, and creates a reference to that module
in the current namespace. Or in other words, after you’ve run this
statement, you can use X.name to refer to things defined in module X.
from X import * imports the module X, and creates references in the
current namespace to all public objects defined by that module (that
is, everything that doesn’t have a name starting with"_"). Or in
other words, after you’ve run this statement, you can simply use a
plain name to refer to things defined in module X. But X itself is not
defined, so X.name doesn’t work. And if name was already defined, it
is replaced by the new version. And if name in X is changed to point
to some other object, your module won’t notice.
from X import a, b, c imports the module X, and creates references in
the current namespace to the given objects. Or in other words, you can
now use a and b and c in your program.
Finally, X = __import__(‘X’) works like import X, with the difference
that you 1) pass the module name as a string, and 2) explicitly assign
it to a variable in your current namespace.
号
顺便说一下，这是你最不感兴趣的方法。
简单地写(例如)：
var ="datetime"
module = __import__(var)
谢谢你的回答清楚明了。
让用户选择要导入的内容可能是一个非常糟糕的主意。包可以在导入时执行代码，因此您实际上允许用户在系统上任意执行代码！这样做更安全
if user_input == 'file1.py':
from files import file1 as file
elif user_input == 'file2.py':
from files import file2 as file
else:
file = None
print"Sorry, you can't import that file"
根据mattjbray的回答：
from importlib import import_module
# lookup in a set is in constant time
safe_names = {"file1.py","file2.py","file3.py", ...}
user_input = ...
if user_input in safe_names:
file = import_module(user_input)
else:
print("Nope, not doing this.")
。
保存几行代码，并允许您以编程方式设置safe_names，或者加载多个模块并将它们分配给dict。