在python中通过ref / by ptr发送?
这个问题在这里已经有了答案:
在某些方面,Python中的所有调用都是通过引用调用的。 事实上,从某种意义上说,所有变量都是引用。 但是有些类型,比如你的例子中的int
,不能改变。
例如,在list
,您要查找的功能很简单:
def change_it(some_list):
some_list.append("world")
foo = ["hello"]
change_it(foo)
print(foo) # prints ['hello', 'world']
但请注意,重新分配参数变量some_list
不会更改调用上下文中的值。
但是,如果你问这个问题,你可能会想用一个函数来设置两个或三个变量。 在这种情况下,你正在寻找这样的东西:
def foo_bar(x, y, z):
return 2*x, 3*y, 4*z
x = 3
y = 4
z = 5
x, y, z = foo_bar(x, y, z)
print(y) # prints 12
当然,你可以用Python做任何事情,但这并不意味着你应该做。 以电视节目Mythbusters的风格,这里有一些你想要的东西
import inspect
def foo(bar):
frame = inspect.currentframe()
outer = inspect.getouterframes(frame)[1][0]
outer.f_locals[bar] = 2 * outer.f_locals[bar]
a = 15
foo("a")
print(a) # prints 30
甚至更糟糕:
import inspect
import re
def foo(bar):
# get the current call stack
my_stack = inspect.stack()
# get the outer frame object off of the stack
outer = my_stack[1][0]
# get the calling line of code; see the inspect module documentation
# only works if the call is not split across multiple lines of code
calling_line = my_stack[1][4][0]
# get this function's name
my_name = my_stack[0][3]
# do a regular expression search for the function call in traditional form
# and extract the name of the first parameter
m = re.search(my_name + "s*(s*(w+)s*)", calling_line)
if m:
# finally, set the variable in the outer context
outer.f_locals[m.group(1)] = 2 * outer.f_locals[m.group(1)]
else:
raise TypeError("Non-traditional function call. Why don't you just"
" give up on pass-by-reference already?")
# now this works like you would expect
a = 15
foo(a)
print(a)
# but then this doesn't work:
baz = foo_bar
baz(a) # raises TypeError
# and this *really*, disastrously doesn't work
a, b = 15, 20
foo_bar, baz = str, foo_bar
baz(b) and foo_bar(a)
print(a, b) # prints 30, 20
请,请, 请不要这样做。 我只是把它放在这里来激发读者去研究Python中一些比较晦涩的部分。
据我所知,这在Python中不存在(尽管如果您将可变对象传递给函数,也会发生类似的情况)。 你也可以做
def test():
global x
x = 3
test()
要么
def test(x):
return 3
x = test(x)
其中第二个更受欢迎。
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