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# -*- coding: utf-8 -*-
from __future__ import absolute_import, print_function, division
# standard library dependencies
import io
from petl.compat import next, PY2, text_type
# internal dependencies
from petl.util.base import Table, asdict
from petl.io.base import getcodec
from petl.io.sources import read_source_from_arg, write_source_from_arg
def fromtext(source=None, encoding=None, errors='strict', strip=None,
header=('lines',)):
"""
Extract a table from lines in the given text file. E.g.::
>>> import petl as etl
>>> # setup example file
... text = 'a,1\\nb,2\\nc,2\\n'
>>> with open('example.txt', 'w') as f:
... f.write(text)
...
12
>>> table1 = etl.fromtext('example.txt')
>>> table1
+-------+
| lines |
+=======+
| 'a,1' |
+-------+
| 'b,2' |
+-------+
| 'c,2' |
+-------+
>>> # post-process, e.g., with capture()
... table2 = table1.capture('lines', '(.*),(.*)$', ['foo', 'bar'])
>>> table2
+-----+-----+
| foo | bar |
+=====+=====+
| 'a' | '1' |
+-----+-----+
| 'b' | '2' |
+-----+-----+
| 'c' | '2' |
+-----+-----+
Note that the strip() function is called on each line, which by default
will remove leading and trailing whitespace, including the end-of-line
character - use the `strip` keyword argument to specify alternative
characters to strip. Set the `strip` argument to `False` to disable this
behaviour and leave line endings in place.
"""
source = read_source_from_arg(source)
return TextView(source, header=header, encoding=encoding,
errors=errors, strip=strip)
class TextView(Table):
def __init__(self, source, header=('lines',), encoding=None,
errors='strict', strip=None):
self.source = source
self.header = header
self.encoding = encoding
self.errors = errors
self.strip = strip
def __iter__(self):
with self.source.open('rb') as buf:
# deal with text encoding
if PY2:
codec = getcodec(self.encoding)
f = codec.streamreader(buf, errors=self.errors)
else:
f = io.TextIOWrapper(buf,
encoding=self.encoding,
errors=self.errors,
newline='')
# generate the table
try:
if self.header is not None:
yield tuple(self.header)
if self.strip is False:
for line in f:
yield (line,)
else:
for line in f:
yield (line.strip(self.strip),)
finally:
if not PY2:
f.detach()
def totext(table, source=None, encoding=None, errors='strict', template=None,
prologue=None, epilogue=None):
"""
Write the table to a text file. E.g.::
>>> import petl as etl
>>> table1 = [['foo', 'bar'],
... ['a', 1],
... ['b', 2],
... ['c', 2]]
>>> prologue = '''{| class="wikitable"
... |-
... ! foo
... ! bar
... '''
>>> template = '''|-
... | {foo}
... | {bar}
... '''
>>> epilogue = '|}'
>>> etl.totext(table1, 'example.txt', template=template,
... prologue=prologue, epilogue=epilogue)
>>> # see what we did
... print(open('example.txt').read())
{| class="wikitable"
|-
! foo
! bar
|-
| a
| 1
|-
| b
| 2
|-
| c
| 2
|}
The `template` will be used to format each row via
`str.format <http://docs.python.org/library/stdtypes.html#str.format>`_.
"""
_writetext(table, source=source, mode='wb', encoding=encoding,
errors=errors, template=template, prologue=prologue,
epilogue=epilogue)
Table.totext = totext
def appendtext(table, source=None, encoding=None, errors='strict', template=None,
prologue=None, epilogue=None):
"""
Append the table to a text file.
"""
_writetext(table, source=source, mode='ab', encoding=encoding,
errors=errors, template=template, prologue=prologue,
epilogue=epilogue)
Table.appendtext = appendtext
def _writetext(table, source, mode, encoding, errors, template, prologue,
epilogue):
# guard conditions
assert template is not None, 'template is required'
# prepare source
source = write_source_from_arg(source, mode)
with source.open(mode) as buf:
# deal with text encoding
if PY2:
codec = getcodec(encoding)
f = codec.streamwriter(buf, errors=errors)
else:
f = io.TextIOWrapper(buf,
encoding=encoding,
errors=errors,
newline='')
# write the table
try:
if prologue is not None:
f.write(prologue)
it = iter(table)
try:
hdr = next(it)
except StopIteration:
hdr = []
flds = list(map(text_type, hdr))
for row in it:
rec = asdict(flds, row)
s = template.format(**rec)
f.write(s)
if epilogue is not None:
f.write(epilogue)
f.flush()
finally:
if not PY2:
f.detach()
def teetext(table, source=None, encoding=None, errors='strict', template=None,
prologue=None, epilogue=None):
"""
Return a table that writes rows to a text file as they are iterated over.
"""
assert template is not None, 'template is required'
return TeeTextView(table, source=source, encoding=encoding, errors=errors,
template=template, prologue=prologue, epilogue=epilogue)
Table.teetext = teetext
class TeeTextView(Table):
def __init__(self, table, source=None, encoding=None, errors='strict',
template=None, prologue=None, epilogue=None):
self.table = table
self.source = source
self.encoding = encoding
self.errors = errors
self.template = template
self.prologue = prologue
self.epilogue = epilogue
def __iter__(self):
return _iterteetext(self.table, self.source, self.encoding,
self.errors, self.template, self.prologue,
self.epilogue)
def _iterteetext(table, source, encoding, errors, template, prologue, epilogue):
# guard conditions
assert template is not None, 'template is required'
# prepare source
source = write_source_from_arg(source)
with source.open('wb') as buf:
# deal with text encoding
if PY2:
codec = getcodec(encoding)
f = codec.streamwriter(buf, errors=errors)
else:
f = io.TextIOWrapper(buf,
encoding=encoding,
errors=errors)
# write the data
try:
if prologue is not None:
f.write(prologue)
it = iter(table)
try:
hdr = next(it)
except StopIteration:
return
yield tuple(hdr)
flds = list(map(text_type, hdr))
for row in it:
rec = asdict(flds, row)
s = template.format(**rec)
f.write(s)
yield row
if epilogue is not None:
f.write(epilogue)
f.flush()
finally:
if not PY2:
f.detach()
|
