Display table nicely in Python with margin and projection (table is a list of dictionary rows)

output.py

################################################################
# Example
################################################################

print("\n# Empty rows list")
show([])

print("\n# Rows list with inconsistent set of columns and margin of 4 spaces")
rows = [
    {"col1": 1, "col2": 2.1, "col3": "long text", "col4": "", "col5": True},
    {"col1": 2, "col2": 3.2, "col3": "def"},
    {"col1": 3, "col2": 4.3334, "col3": "ghi", "col4": None}
]
show(rows, margin=4)

print("\n# Rows with different value types and enforced column order")
rows = [
    {"sdate": "2015-01-01", "min": 1.0234, "max": 3935.234, "mean": 1.2, "std": "NaN"},
    {"sdate": "2015-01-02", "min": 1.234, "max": 234.2, "mean": 34.2, "std": "NaN"},
    {"sdate": "2015-01-03", "min": 1.0, "max": 3.8, "mean": 2.3, "std": "NaN"},
    {"sdate": "2015-01-04", "min": 2.04, "max": 810.34, "mean": 789.32, "std": "NaN"},
    {"sdate": "2015-01-05", "min": "NaN", "max": "NaN", "mean": 0.001, "std": "NaN"}
]
show(rows, columns=["sdate", "min", "max", "mean", "std"])
show(rows, margin=4, columns=["sdate", "mean"])

"""

# Empty rows list
++
||
++
++

# Rows list with inconsistent set of columns and margin of 4 spaces
    +-----+-----+-------+----------+-----+
    | col4| col5|   col2|      col3| col1|
    +-----+-----+-------+----------+-----+
    |     | True|    2.1| long text|    1|
    |     |     |    3.2|       def|    2|
    | None|     | 4.3334|       ghi|    3|
    +-----+-----+-------+----------+-----+

# Rows with different value types and enforced column order
+-----------+-------+---------+-------+----+
|      sdate|    min|      max|   mean| std|
+-----------+-------+---------+-------+----+
| 2015-01-01| 1.0234| 3935.234|    1.2| NaN|
| 2015-01-02|  1.234|    234.2|   34.2| NaN|
| 2015-01-03|    1.0|      3.8|    2.3| NaN|
| 2015-01-04|   2.04|   810.34| 789.32| NaN|
| 2015-01-05|    NaN|      NaN|  0.001| NaN|
+-----------+-------+---------+-------+----+
    +-----------+-------+
    |      sdate|   mean|
    +-----------+-------+
    | 2015-01-01|    1.2|
    | 2015-01-02|   34.2|
    | 2015-01-03|    2.3|
    | 2015-01-04| 789.32|
    | 2015-01-05|  0.001|
    +-----------+-------+
"""

table.py

#!/usr/bin/python

def table(rows, margin=0, columns=[]):
    """
    Return string representing table content, returns table as string and as a list of strings.
    It is okay for rows to have different sets of keys, table will show union of columns with
    missing values being empty spaces.

    :param rows: list of dictionaries as rows
    :param margin: left space padding to apply to each row, default is 0
    :param columns: extract listed columns in provided order, other columns will be ignored
    :return: table content as string and as list
    """
    def projection(cols, columns):
        return [(x, cols[x]) for x in columns if x in cols] if columns else cols.items()
    def row_to_string(row, columns):
        values = [(row[name] if name in row else "").rjust(size) for name, size in columns]
        return "|%s|" % ("|".join(values))
    def header(columns):
        return "|%s|" % ("|".join([name.rjust(size) for name, size in columns]))
    def divisor(columns):
        return "+%s+" % ("+".join(["-" * size for name, size in columns]))
    data = [dict([(str(a), str(b)) for a, b in row.items()]) for row in rows]
    cols = dict([(x, len(x) + 1) for row in data for x in row.keys()]) if data else {}
    for row in data:
        for key in row.keys():
            cols[key] = max(cols[key], len(row[key]) + 1)
    proj = projection(cols, columns) # extract certain columns to display (or all if not provided)
    table = [divisor(proj), header(proj), divisor(proj)] + \
        [row_to_string(row, proj) for row in data] + [divisor(proj)]
    table = ["%s%s" % (" " * margin, tpl) for tpl in table] if margin > 0 else table
    table_text = "\n".join(table)
    return (table_text, table)

def show(rows, margin=0, columns=[]):
    """
    Print table in console for list of rows.
    """
    txt, _ = table(rows, margin, columns)
    print(txt)