shebang line python

1That is called the shebang line. As the Wikipedia entry explains:
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3In computing, a shebang (also called a hashbang, hashpling, pound bang, or crunchbang) refers to the characters "#!" when they are the first two characters in an interpreter directive as the first line of a text file. In a Unix-like operating system, the program loader takes the presence of these two characters as an indication that the file is a script, and tries to execute that script using the interpreter specified by the rest of the first line in the file.
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5See also the Unix FAQ entry.
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7Even on Windows, where the shebang line does not determine the interpreter to be run, you can pass options to the interpreter by specifying them on the shebang line. I find it useful to keep a generic shebang line in one-off scripts (such as the ones I write when answering questions on SO), so I can quickly test them on both Windows and ArchLinux.
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9The env utility allows you to invoke a command on the path:
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11The first remaining argument specifies the program name to invoke; it is searched for according to the PATH environment variable. Any remaining arguments are passed as arguments to that program.