3.4. Specifying Single Files Vs. Lists of Files
We've now shown you two ways to specify the source for a program, one with a list of files:
Program('hello', ['file1.c', 'file2.c'])
And one with a single file:
Program('hello', 'hello.c')
You could actually put a single file name in a list, too, which you might prefer just for the sake of consistency:
Program('hello', ['hello.c'])
SCons functions will accept a single file name in either form. In fact, internally, SCons treats all input as lists of files, but allows you to omit the square brackets to cut down a little on the typing when there's only a single file name.
 | Although SCons functions are forgiving about whether or not you use a string vs. a list for a single file name, Python itself is more strict about treating lists and strings differently. So where SCons allows either a string or list:
# The following two calls both work correctly:
Program('program1', 'program1.c')
Program('program2', ['program2.c'])
Trying to do "Python things" that mix strings and lists will cause errors or lead to incorrect results:
common_sources = ['file1.c', 'file2.c']
# THE FOLLOWING IS INCORRECT AND GENERATES A PYTHON ERROR
# BECAUSE IT TRIES TO ADD A STRING TO A LIST:
Program('program1', common_sources + 'program1.c')
# The following works correctly, because it's adding two
# lists together to make another list.
Program('program2', common_sources + ['program2.c'])
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