Define generic for pretty-printing objects inside a table. (#12)

* Define generic for pretty-printing objects inside a table.

Also define a function for formatting a table, so that we don't
have to rely on third-party libraries for our pretty-printing.

Author: LTLA

src/biocgenerics/__init__.py

@@ -20,3 +20,4 @@
 from .combine_cols import combine_cols
 from .combine_rows import combine_rows
 from .rownames import rownames, set_rownames
+from .show_as_cell import show_as_cell, format_table

src/biocgenerics/show_as_cell.py

@@ -0,0 +1,113 @@
+from functools import singledispatch
+from typing import Any, List, Optional, Sequence
+
+__author__ = "Aaron Lun"
+__copyright__ = "LTLA"
+__license__ = "MIT"
+
+
+@singledispatch
+def show_as_cell(x: Any, indices: Sequence[int]) -> List[str]:
+    """Show the contents of ``x`` as a cell of a table, typically for use in the ``__str__`` method of a class that
+    contains ``x``.
+
+    Args:
+        x:
+            Any object. By default, we assume that it can be treated as
+            a sequence, with a valid ``__getitem__`` method for an index.
+
+        indices:
+            List of indices to be extracted.
+
+    Returns:
+        List of strings of length equal to ``indices``, containing a
+        string summary of each of the specified elements of ``x``.
+    """
+    output = []
+    for i in indices:
+        output.append(str(x[i]))
+    return output
+
+
+def _get_max_width(col: List[str]):
+    width = 0
+    for y in col:
+        if len(y) > width:
+            width = len(y)
+    return width
+
+
+def format_table(
+    columns: List[Sequence[str]],
+    floating_names: Optional[Sequence[str]] = None,
+    sep: str = " ",
+    window: Optional[int] = None,
+) -> str:
+    """Pretty-print a table with wrapping columns.
+
+    Args:
+        columns: List of list of strings, where each inner list is the same length.
+            Strings are typically generated by :py:meth:`~show_as_cell`.
+
+        floating_names: List of strings to be added to the left of the table. This is
+            printed repeatedly for each set of wrapped columns.
+
+        sep: Separator between columns.
+
+        window: Size of the terminal window, in characters. We attempt to determine
+            this automatically, otherwise it is set to 150.
+
+    Returns:
+        str: String containing the pretty-printed table.
+    """
+    if window is None:
+        import os
+
+        try:
+            window = os.get_terminal_size().columns
+        except Exception as _:
+            window = 150
+
+    if len(columns) == 0:
+        raise ValueError("At least one column should be supplied in 'columns'.")
+    n = len(columns[0])
+
+    floatwidth = 0
+    if floating_names is not None:
+        floatwidth = _get_max_width(floating_names)
+        new_floating_names = []
+        for y in floating_names:
+            new_floating_names.append(y.rjust(floatwidth))
+        floating_names = new_floating_names
+
+    output = ""
+
+    def reinitialize():
+        if floating_names is None:
+            return [""] * n
+        else:
+            return floating_names[:]
+
+    contents = reinitialize()
+    init = True
+    used = floatwidth
+
+    for col in columns:
+        width = _get_max_width(col)
+
+        if not init and used + width + len(sep) > window:
+            for line in contents:
+                output += line + "\n"
+            contents = reinitialize()
+            init = True
+            used = floatwidth
+
+        for i, y in enumerate(col):
+            if used > 0:
+                contents[i] += sep
+            contents[i] += y.rjust(width)
+        used += width + len(sep)
+        init = False
+
+    output += "\n".join(contents)
+    return output

tests/test_show_as_cell.py

@@ -0,0 +1,22 @@
+from biocgenerics import show_as_cell, format_table
+
+
+def test_show_as_cell():
+    assert show_as_cell([1, 2, 3, 4], range(4)) == ["1", "2", "3", "4"]
+    assert show_as_cell([1, 2, 3, 4], [1, 3]) == ["2", "4"]
+
+
+def test_format_table():
+    contents = [
+        ["asdasd", "1", "2", "3", "4"],
+        [""] + ["|"] * 4,
+        ["asyudgausydga", "A", "B", "C", "D"],
+    ]
+    print(format_table(contents))
+    print(format_table(contents, floating_names=["", "aarg", "boo", "ffoo", "stuff"]))
+    print(format_table(contents, window=10))
+    print(
+        format_table(
+            contents, window=10, floating_names=["", "AAAR", "BBBB", "XXX", "STUFF"]
+        )
+    )