psxls psxls - 4 months ago 12
Python Question

How to Pretty Print a CSV file in Python

How can I pretty print a CSV file using Python, not any external tool?

For example I have this CSV file:

title1|title2|title3|title4
datalongdata|datalongdata|data|data

data|data|data|datalongdatadatalongdatadatalongdatadatalongdatadatalongdata
data|data'data|dat


I would like to transform it to visually look like a table. For example, to something like that:

+ --------------------------------------------------------------------------------------------------- +
| title1 | title2 | title3 | title4 |
+ --------------------------------------------------------------------------------------------------- +
| datalongdata | datalongdata | data | data |
| | | | |
| data | data | data | datalongdatadatalongdatadatalongdatadatalongdatadatalongdata |
| data | data'data | dat | |
+ --------------------------------------------------------------------------------------------------- +

Answer

Usage:

pretty.pretty_file(filename, ***options*)

Reads a CSV file and prints visually the data as table to a new file. filename, is the given CSV file. The optional ***options* keyword arguments is the union of Python's Standard Library csv module Dialects and Formatting Parameters and the following list:

  • new_delimiter: the new column separator (default " | ")
  • border: boolean value if you want to print the border of the table (default True)
  • border_vertical_left: the left border of the table (default "| ")
  • border_vertical_right: the right border of the table (default " |")
  • border_horizontal: the top and bottom border of the table (default "-")
  • border_corner_tl: the top-left corner of the table (default "+ ")
  • border_corner_tr: the top-right corner of the table (default " +")
  • border_corner_bl: the bottom-left corner of the table (default same as border_corner_tl)
  • border_corner_br: the bottom-right corner of the table (default same as border_corner_tr)
  • header: boolean value if the first row is a table header (default True)
  • border_header_separator: the border between the header and the table (default same as border_horizontal)
  • border_header_left: the left border of the table header (default same as border_corner_tl)
  • border_header_right: the right border of the table header (default same as border_corner_tr)
  • new_filename: the new file's filename (default "new_" + filename)
  • newline: defines how the rows of the table will be separated (default "\n")

Example:

import pretty_csv
pretty_csv.pretty_file("test.csv", header=False, border=False, delimiter="|")

Python 3:

This is a Python 2 implementation. For Python 3, you have to change the 2 occurrences of the line open(filename, "rb") as input: to open(filename, "r", newline="") as input: since csv.reader in Python 3 wants the file to be opened in text mode.

Module:

import csv

def pretty_file(filename, **options):
    """
    @summary:
        Reads a CSV file and prints visually the data as table to a new file.
    @param filename:
        is the path to the given CSV file.
    @param **options:
        the union of Python's Standard Library csv module Dialects and Formatting Parameters and the following list:
    @param new_delimiter:
        the new column separator (default " | ")
    @param border:
        boolean value if you want to print the border of the table (default True)
    @param border_vertical_left:
        the left border of the table (default "| ")
    @param border_vertical_right:
        the right border of the table (default " |")
    @param border_horizontal:
        the top and bottom border of the table (default "-")
    @param border_corner_tl:
        the top-left corner of the table (default "+ ")
    @param border_corner_tr:
        the top-right corner of the table (default " +")
    @param border_corner_bl:
        the bottom-left corner of the table (default same as border_corner_tl)
    @param border_corner_br:
        the bottom-right corner of the table (default same as border_corner_tr)
    @param header:
        boolean value if the first row is a table header (default True)
    @param border_header_separator:
        the border between the header and the table (default same as border_horizontal)
    @param border_header_left:
        the left border of the table header (default same as border_corner_tl)
    @param border_header_right:
        the right border of the table header (default same as border_corner_tr)
    @param newline:
        defines how the rows of the table will be separated (default "\n")
    @param new_filename:
        the new file's filename (*default* "/new_" + filename)
    """

    #function specific options
    new_delimiter           = options.pop("new_delimiter", " | ")
    border                  = options.pop("border", True)
    border_vertical_left    = options.pop("border_vertical_left", "| ")
    border_vertical_right   = options.pop("border_vertical_right", " |")
    border_horizontal       = options.pop("border_horizontal", "-")
    border_corner_tl        = options.pop("border_corner_tl", "+ ")
    border_corner_tr        = options.pop("border_corner_tr", " +")
    border_corner_bl        = options.pop("border_corner_bl", border_corner_tl)
    border_corner_br        = options.pop("border_corner_br", border_corner_tr)
    header                  = options.pop("header", True)
    border_header_separator = options.pop("border_header_separator", border_horizontal)
    border_header_left      = options.pop("border_header_left", border_corner_tl)
    border_header_right     = options.pop("border_header_right", border_corner_tr)
    newline                 = options.pop("newline", "\n")

    file_path = filename.split(os.sep)
    old_filename = file_path[-1]
    new_filename            = options.pop("new_filename", "new_" + old_filename)

    column_max_width = {} #key:column number, the max width of each column
    num_rows = 0 #the number of rows

    with open(filename, "rb") as input: #parse the file and determine the width of each column
        reader=csv.reader(input, **options)
        for row in reader:
            num_rows += 1
            for col_number, column in enumerate(row):
                width = len(column)
                try:
                    if width > column_max_width[col_number]:
                        column_max_width[col_number] = width
                except KeyError:
                    column_max_width[col_number] = width

    max_columns = max(column_max_width.keys()) + 1 #the max number of columns (having rows with different number of columns is no problem)

    if max_columns > 1:
        total_length = sum(column_max_width.values()) + len(new_delimiter) * (max_columns - 1)
        left = border_vertical_left if border is True else ""
        right = border_vertical_right if border is True else ""
        left_header = border_header_left if border is True else ""
        right_header = border_header_right if border is True else ""

        with open(filename, "rb") as input:
            reader=csv.reader(input, **options)
            with open(new_filename, "w") as output:
                for row_number, row in enumerate(reader):
                    max_index = len(row) - 1
                    for index in range(max_columns):
                        if index > max_index:
                            row.append(' ' * column_max_width[index]) #append empty columns
                        else:
                            diff = column_max_width[index] - len(row[index])
                            row[index] = row[index] + ' ' * diff #append spaces to fit the max width

                    if row_number==0 and border is True: #draw top border
                        output.write(border_corner_tl + border_horizontal * total_length + border_corner_tr + newline)
                    output.write(left + new_delimiter.join(row) + right + newline) #print the new row
                    if row_number==0 and header is True: #draw header's separator
                        output.write(left_header + border_header_separator * total_length + right_header + newline)
                    if row_number==num_rows-1 and border is True: #draw bottom border
                        output.write(border_corner_bl + border_horizontal * total_length + border_corner_br)
Comments