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=== Benefits of using a function instead of a statement === * Extended call syntax provides better interaction with sequences * Keyword argument `sep` allows separator to be changed easily and obviously * Keyword argument `end` allows line terminator to be changed easily and obviously * Keyword argument `stream` allows easy and obvious redirection * Builtin can be replaced for easy customisation (e.g. per-thread logging) * Interacts well with new PEP 309 partial function application === Sample implementation === This is a Python 2.4 compatible sample implementation, which is why it uses the name `output` rather than `print`. {{{#!python def output(*args, **kwds): """Functional replacement for the print statement >>> output(1, 2, 3) 1 2 3 >>> output(1, 2, 3, sep='') 123 >>> output(1, 2, 3, sep=', ') 1, 2, 3 >>> output(1, 2, 3, end='Alternate line ending') 1 2 3Alternate line ending >>> import sys >>> output(1, 2, 3, stream=sys.stderr) 1 2 3 >>> output(*range(10)) 0 1 2 3 4 5 6 7 8 9 >>> output(*(x*x for x in range(10))) 0 1 4 9 16 25 36 49 64 81 """ # Parse the keyword-only optional arguments defaults = { "sep": " ", "end": "\n", "stream": sys.stdout, } for name, default in defaults.items(): item = None try: item = kwds[name] except KeyError: pass if item is None: kwds[name] = default sep, end, stream = kwds["sep"], kwds["end"], kwds["stream"] # Perform the print operation without building the whole string for arg in args[:1]: stream.write(str(arg)) for arg in args[1:]: stream.write(sep) stream.write(str(arg)) stream.write(end) }}} |
This page discusses the benefits of replacing the current print statement with an equivalent builtin. The output function presented below does everything the print statement does without requiring an hacking of the grammar, and also makes a number of things significantly easier.
Benefits of using a function instead of a statement
- Extended call syntax provides better interaction with sequences
Keyword argument sep allows separator to be changed easily and obviously
Keyword argument end allows line terminator to be changed easily and obviously
Keyword argument stream allows easy and obvious redirection
- Builtin can be replaced for easy customisation (e.g. per-thread logging)
- Interacts well with new PEP 309 partial function application
Sample implementation
This is a Python 2.4 compatible sample implementation, which is why it uses the name output rather than print.
1 def output(*args, **kwds):
2 """Functional replacement for the print statement
3
4 >>> output(1, 2, 3)
5 1 2 3
6 >>> output(1, 2, 3, sep='')
7 123
8 >>> output(1, 2, 3, sep=', ')
9 1, 2, 3
10 >>> output(1, 2, 3, end='Alternate line ending')
11 1 2 3Alternate line ending
12 >>> import sys
13 >>> output(1, 2, 3, stream=sys.stderr)
14 1 2 3
15 >>> output(*range(10))
16 0 1 2 3 4 5 6 7 8 9
17 >>> output(*(x*x for x in range(10)))
18 0 1 4 9 16 25 36 49 64 81
19 """
20 # Parse the keyword-only optional arguments
21 defaults = {
22 "sep": " ",
23 "end": "\n",
24 "stream": sys.stdout,
25 }
26 for name, default in defaults.items():
27 item = None
28 try:
29 item = kwds[name]
30 except KeyError:
31 pass
32 if item is None:
33 kwds[name] = default
34 sep, end, stream = kwds["sep"], kwds["end"], kwds["stream"]
35 # Perform the print operation without building the whole string
36 for arg in args[:1]:
37 stream.write(str(arg))
38 for arg in args[1:]:
39 stream.write(sep)
40 stream.write(str(arg))
41 stream.write(end)