CODEWITHSUNDEEP
pythonimport
Richard
Richard

Reputation: 15862

importing classes python

Just wondering why 

import sys
exit(0)

gives me this error:

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in ?
    exit(0)
TypeError: 'str' object is not callable

but

from sys import exit
exit(0)

works fine?

Upvotes: 3

Views: 702

Answers (3)

Richard
Richard

Reputation: 15862

Ok from your Answers I can remeber that:

import sys from *

would import all members from sys

Upvotes: 0

FogleBird
FogleBird

Reputation: 76762

See http://effbot.org/zone/import-confusion.htm for all the different ways to use import in Python.

import sys

This imports the sys module and binds it to the name "sys" in your namespace. "exit", and other members of the sys module are not brought into the namespace directly but can be accessed like so:

sys.exit(0)

from sys import exit

This imports specific members of the sys module into your namespace. Specifically this binds the name "exit" to the sys.exit function.

exit(0)

To see what's in your namespace, use the dir function.

>>> import sys
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'sys']
>>>
>>> from sys import exit
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'exit', 'sys']

You can even see what all is in the sys module itself:

>>> dir(sys)
['__displayhook__', '__doc__', '__egginsert', '__excepthook__', '__name__', '__package__', '__plen', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dllhandle', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'flags', 'float_info', 'getcheckinterval', 'getdefaultencoding', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'getwindowsversion', 'hexversion', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'py3kwarning', 'setcheckinterval', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions', 'winver']

Upvotes: 6

lprsd
lprsd

Reputation: 87077

Python imports only the chosen names into the namespace.

Your equivalent first solution should be

sys.exit(0)

since import sys imports only the sys keyword into the current namespace.

Upvotes: 8

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