激活之后变了哪两样

运行下面这段程序，填写它打印出来的结果。

BEFORE = {"VIRTUAL_ENV": "", "PATH": "/usr/local/bin:/usr/bin"}
AFTER = {"VIRTUAL_ENV": "/home/me/.venv",
         "PATH": "/home/me/.venv/bin:/usr/local/bin:/usr/bin"}
changed = sorted(k for k in BEFORE if BEFORE[k] != AFTER[k])
print(str(len(changed)) + "/" + ",".join(changed) + "/"
      + AFTER["PATH"].split(":")[0])