在较新版本（> 1.x）中有一个pip.operation.freeze：
try: from pip._internal.operations import freezeexcept importError: # pip < 10.0 from pip.operations import freezex = freeze.freeze()for p in x: print p
输出是预期的：
amqp == 1.4.6
anyjson == 0.3.3
台球== 3.3.0.20
defusedxml == 0.4.1
Django == 1.8.1
django-picklefield == 0.3.1
docutils == 0.12
…等
