Python rstrip and whitespace

Was just reading

https://www.w3schools.com/python/ref_string_rstrip.asp

which says

The rstrip() method removes any trailing characters (characters at the end a string), space is the default trailing character to remove.

Notes:

1) the chars param was added at Python 2.2.3, can’t use it at older versions as noted at

https://docs.python.org/2.6/library/string.html

string.rstrip(s[, chars])

Return a copy of the string with trailing characters removed. If chars is omitted or None, whitespace characters are removed. If given and not None, chars must be a string; the characters in the string will be stripped from the end of the string this method is called on.

Changed in version 2.2.3: The chars parameter was added. The chars parameter cannot be passed in earlier 2.2 versions.

2) from the official doc and other docs too I read the default is to remove whitespace characters, not just the space char:

https://python-reference.readthedocs.io/en/latest/docs/str/rstrip.html

chars

Optional. String specifying the set of characters to be removed. If omitted or None, the chars argument defaults to removing whitespace. The chars argument is not a prefix; rather, all combinations of its values are stripped.

Not sure what is considered whitespace in various Python versions though. At least in Python2 it wasn’t removing \r in both Solaris and MSYS2 (a POSIX environment on Windows) where I just tried.

For example, I was just debugging some program that was working in Python 3, but in Python 2 it was moving the cursor to the start of the line when printing a raw_input prompt with some string it had read before…
…the issue proved to be that it was opening a file with ‘r’ mode instead of ‘rU’ which is universal newlines mode – https://www.python.org/dev/peps/pep-0278/ – converts \r\n to \n – and it seems that rstrip was failing to remove the \r from the end of those strings.

In Python 3 it was either using the universal newlines mode by default and thus stripping the \r from strings while reading from the file, or the rstrip was removing \r too in Python3, but I guess it was the 1st case (didn’t do any more check since the universal newlines read file open mode fixed the issue in Python 2 for me).

Speaking of that, I wonder whether Python considers whitespace differently on Windows and on Unixes (aka having [l/r]strip commands remove \r on the 1st but not on the 2nd case), which would be an extra complexity when writing portable s/w.

HowTo: Insert new line and spacing at content of WPF TextBlock control

While adding more voice commands at SpeechTurtle, I had to update the active legend where the available commands are displayed and their text is highlighted as the respective commands are recognized by the speech recognition engine (using .NET’s managed Speech API).

A problem I faced was how to add a newline and prefixing the 2nd line with some spaces to align with the first command at the 1st line…

First of all, adding a new line was easy, inserted a <LineBreak /> tag in the XAML inside the TextBlock tag’s content, as shown in the screenshot below:

Then I had the issue that I needed to add some spacing so that “Pen up” at the 2nd line starts exactly under the start of “Forward” at the 1st line (see screenshot above)…

Tried to add a Run tag, with its Text set to some spaces, but couldn’t get an exact positioning:

So I tried using a Separator instead, since I could define a Width for it, however, it was drawing as a gray line:

So I either had to change its color to White or Transparent, or use a Null Foreground Brush on it (one difference of a Null brush from a Transparent one is that the element ignores Mouse events in that case from what I remember), or just set its Visibility mode to Hidden:

Do note that WPF has another visibility mode apart from Visible and Hidden, that is Collapsed, where the respective control disappears from the layout flow (that value is not supported in Silverlight from what I remember), which is not what we wanted in this case (Hidden was the correct option to choose):