在调用Python脚本时，“。/ script.py”和“python script.py”之间有什么区别

Question

One difference is that "./script.py" only works if script.py is executable (as in file permissions), but "python script.py" works regardless. However, I strongly suspect there are more differences, and I want to know what they are.

I have a Django website, and "python manage.py syncdb" works just fine, but "./manage.py syncdb" creates a broken database for some reason that remains a mystery to me. Maybe it has to do with the fact that syncdb prompts for a superuser name and password from the command line, and maybe using "./manage.py syncdb" changes the way it interacts with the command line, thus mangling the password. Maybe? I am just baffled by this bug. "python manage.py syncdb" totally fixes it, so this is just curiosity.

Thanks.

Edit: Right, right, I forgot about the necessity of the shebang line #!/usr/bin/python. But I just checked, "python manage.py syncdb" and "./manage.py syncdb" are using the same Python interpreter (2.7.2, the only one installed, on Linux Mint 12). Yet the former works and the latter does not.

Could the environment variables seen by the Python code be different? My code does require $LD_LOADER_PATH and $PYTHON_PATH to be set special for each shell.

Answer 1

Calling ./script.py uses the "shebang line" in the script to determine which interpreter to use to run the script. Such a line might look like

#!/usr/bin/env python

or

#!/usr/bin/python2.7

or whatever path to the python interpreter is used. If it resolves to the same Python interpreter that is called by just

python

from the shell command line, there is no difference between ./script.py and python script.py , but the two version can end up using different Python interpreters.

Answer 2

./script.py = "Attempt to execute a file called script.py in the current shell"

python script.py = "Send script.py as an argument to the first python executable in the current $PATH "

The first only works if the file has the execute bit set for the user attempting to execute the file and it has the so-called shebang line, which tells the shell how to run it.

Answer 3

./script.py runs the interpreter defined in the #! at the beginning of the file. For example, the first line might be #! /usr/bin/env python #! /usr/bin/env python or #! /usr/bin/python #! /usr/bin/python or something else like that. If you look at what interpreter is invoked, you might be able to fix that problem.

Answer 4

In Linux using terminal you can execute any file -if the user has execute permission- by typing ./fileName . When the OS sees a valid header like #! /usr/bin/python #! /usr/bin/python (or for perl #! /usr/bin/python ), It will call the python or perl (appropriate) interpreter to execute the program. You can use the command python script.py directly because, python is a executable program located at /usr/bin (or somewhere else) which is in a environmental variable $PATH, that corresponding to directory of executables.