# View a sequence of columns as a table:

import petl as etl
cols = [[0, 1, 2], ['a', 'b', 'c']]
tbl = etl.fromcolumns(cols)
tbl

# If columns are not the same length, values will be padded to the length of the longest column with missing, which is None by default:

cols = [[0, 1, 2], ['a', 'b']]
tbl = etl.fromcolumns(cols, missing='NA')
tbl

# petl.io.csv.fromcsv(source=None, encoding=None, errors='strict', header=None, **csvargs)
# Extract a table from a delimited file:

import csv
table1 = [['foo', 'bar'],
          ['a', 1],
          ['b', 2],
          ['c', 2]]
with open('example.csv', 'w') as f:
    writer = csv.writer(f)
    writer.writerows(table1)
    
table2 = etl.fromcsv('example.csv'); table2

# The “to…” functions load data from a table into a file-like source or database. 
# For functions that accept a source argument, if the source argument is None or a string it is interpreted as follows:
# None - write to stdout
# string ending with .gz or .bgz - write to file via gzip decompression
# string ending with .bz2 - write to file via bz2 decompression
# any other string - write directly to file


# Write the table to a CSV file:

etl.tocsv(table1, 'example.csv')
print(open('example.csv').read())

table1 = etl.fromcolumns(table1); table1

# Extract a table from data pickled in the given file. The rows in the table should have been pickled to the file one at a time:

import pickle

with open('example.p', 'wb') as f:
    pickle.dump(['foo', 'bar'], f)
    pickle.dump(['a', 1], f)
    pickle.dump(['b', 2], f)
    pickle.dump(['c', 2.5], f)
table1 = etl.frompickle('example.p')
table1

# Write the table to a pickle file:

import petl as etl
table1 = [['foo', 'bar'],
['a', 1],
['b', 2],
['c', 2]]
etl.topickle(table1, 'example.p')
table2 = etl.frompickle('example.p')
table2

# Extract a table from lines in the given text file:
import petl as etl
text = 'a,1\nb,2\nc,2\n'
with open('example.txt', 'w') as f:
    f.write(text)
    
table1 = etl.fromtext('example.txt'); table1    

# post-process, e.g., with capture()
table2 = table1.capture('lines', '(.*),(.*)$', ['foo', 'bar']); table2

# Write the table as HTML to a file:
import petl as etl
table1 = [['foo', 'bar'],
['a', 1],
['b', 2],
['c', 2]]
etl.tohtml(table1, 'example.html', caption='example table')
print(open('example.html').read())