pandas IPython - 有打印默认打印头和尾长变量
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IPython - have print default to print head & tail on long variables
提问by schodge
(For working in IPython only, either terminal or QTConsole, not Notebook) Is there a way to make a regular print statement (yes, 2.7) automatically print the head and tail (or even just the head) of a variable if it is over some arbitrary size?
（仅适用于 IPython，终端或 QTConsole，而不是 Notebook）有没有办法使常规打印语句（是的，2.7）自动打印变量的头部和尾部（甚至只是头部），如果它结束了一些任意大小？
If I print dataframeon a pandas dataframe that is too big, pandas automatically just prints the head. I'd like it work that way on lists and numpy arrays too, so that the next time I accidentally print a giant array out by accident I don't wind up with 100 pages of numbers. (I'm sure I could write a function to do this, but I reflexively use print, so I'm wondering if there's a way to control how much IPython will display - really, I'd rather change what the console displays instead of what the program is doing.)
如果我print dataframe在太大的Pandas数据帧上，Pandas会自动打印头部。我也希望它在列表和 numpy 数组上也能这样工作，这样下次我不小心打印出一个巨大的数组时，我就不会得到 100 页的数字。（我确定我可以编写一个函数来执行此操作，但我会条件反射地使用打印，所以我想知道是否有办法控制 IPython 将显示多少 - 实际上，我宁愿更改控制台显示的内容而不是程序在做什么。）
采纳答案by Dima Tisnek
You can't really do much with printstatement, but you can do something about ipython's output, consider these to commands:
你真的不能用printstatement做太多事情，但是你可以对ipython的输出做一些事情，考虑这些命令：
In [13]: x = range(3)
In [14]: x
Out[14]: [0, 1, 2]
In [15]: print x
[0, 1, 2]
First, xassigns Out[14]to value of the expression and that Out[14]is then displayed.
首先，x分配Out[14]给表达式的值，Out[14]然后显示。
You can hack ipythonto display it differently. From what I can tell, ipythonuses pprintinternally or a copy thereof. Simply monkey-patching pprint.pprint/pprint.pformat/pprint.PrettyPrinterdoesn't work though. You'd need to hack ipython proper.
你可以破解ipython以不同的方式显示它。据我所知，内部ipython使用pprint或其副本。不过，简单的猴子修补pprint.pprint/pprint.pformat/pprint.PrettyPrinter是行不通的。你需要正确地破解 ipython。
Second, print xgoes straight to the heart of Python. In python 2.x you cannot change what printdoes. In python 3.x print()is just a function and you can monkey-patch it.
其次，print x直击 Python 的核心。在 python 2.x 中，你不能改变什么print。在 python 3.xprint()中只是一个函数，你可以给它打补丁。
If what you print is a object of your own class, feel free to redefine __str__and __repr__like numpy does:
如果您打印的是您自己的类的对象，请随意重新定义__str__并__repr__像 numpy 一样：
numpy.set_printoptions(threshold=2)
numpy.array(range(10)).__str__()
'[0 1 2 ..., 7 8 9]'
print numpy.array(range(10))
[0 1 2 ..., 7 8 9]
Finally, ipythoncomes with %pagemagic command, you can issue %page xand if representation of xis large enough, you'll be dropped to lessor similar pager where you can view this text representation one page at a time.
最后，ipython附带%page魔术命令，您可以发出%page x，如果表示x足够大，您将被放置到less或类似的寻呼机，您可以一次一页地查看此文本表示。
P.S. ipythonis extensible via "traits," it's still back magic for me, but perhaps you can solve first case using traits.
PSipython可以通过“特征”进行扩展，对我来说它仍然是魔法，但也许您可以使用特征来解决第一种情况。
