Console-width detection should be interactive sessions only

[dandavison]

I was surprised to see that my program's standard output changed when I unplugged my laptop from my external display this afternoon! I suggest that the terminal-width detection feature should only operate in an interactive python session. In non-interactive usage the stdout should depend only on the print options currently in effect.

See PR #453

[lodagro]

Auto detection of the terminal width is a print option set by default. It can be disabled by setting max_columns to a non zero value.

pandas.set_printoptions(max_columns=10)

Idea behind the auto detection is to determine if the full string representation of a series or dataframe fits in the terminal (either in width/height or both). If it does not fit a summary view will be displayed. Fit or not is independent if you run from interactive shell or not, so why ignore it?

[dandavison]

What I'm saying is basically that it is un-UNIXy for the stdout of a shell command to depend on the dimensions of the terminal. (ls is a well-known exception.)

In fact I think there is one clear argument that there is a bug here: the behavior persists even when redirecting the stdout to a file. That should definitely not happen by default; when redirecting stdout to a file, the resulting contents of that file should not depend on current terminal dimensions. (That's true even for ls .)

[lodagro]

Indeed, by default pandas always checks terminal width, which impacts output. However user/user-code is in full control and can change this behavior if desired, potentially based on interactive/non interactive use.

[dandavison]

Right. I propose changing the default so that non-interactive use does not check terminal width.

(I don't propose making it impossible for users to have terminal-width-detection in non-interactive mode.)

[lodagro]

What i meant by user/user-code is in full control is that you can determine in your script/code when you want to use or disable auto detect of terminal width. Without changing pandas internals you can have the desired behavior.

[dandavison]

Right, but I am saying that the pandas default is wrong: by default, without having to change any options, output to file from a python program should not depend on terminal width. So a code change to pandas would be required to fix that.

close?

[wesm]

yep