* In module text_input: Added head() and tail() to emulate the basic

behavior of UNIX commands with the same name.
  Output lines are already split into a list of strings.
master
Wirawan Purwanto 13 years ago
parent 41079fd92c
commit 6656d3d5e3
  1. 51
      iofmt/text_input.py

@ -40,7 +40,13 @@ class text_input(object):
etc.
To support more fancy options (e.g., rewinding), use "superize=1" when
creating the instance.'''
creating the instance.
Other valid constructor flags:
- expand_errorbar (default: False)
- comment_char (default: "#")
- skip_blank_lines (default: True)
'''
def __init__(self, fname, **opts):
if opts.get("superize", 0):
@ -258,3 +264,46 @@ class text_input(object):
# A hook for field_filtering_proc for expanding errorbars:
from pyqmc.stats.errorbar import expand
return expand(F, flatten=True)
# Various sundry tools
def head(filename, maxlines):
"""Emulates UNIX head(1) command by reading at most `maxlines`
text lines.
It is intended for plain text files only!
It also supports compressed files through text_input() facility.
"""
# head is easy to implement. But how about tail?
F = text_input(filename, skip_blank_lines=False, comment_char='\0')
out = []
try:
for x in xrange(maxlines):
out.append(F.next())
except StopIteration:
pass
return out
def tail(filename, maxlines):
"""Emulates UNIX tail(1) command by reading at most `maxlines`
text lines at the end of a text file.
It is intended for plain text files only!
It also supports compressed files through text_input() facility.
Warning: this algorithm is far less optimal than head() since it
has to read the whole file.
It's okay for moderately small files.
"""
F = text_input(filename, skip_blank_lines=False, comment_char='\0')
out = []
lines2read = max(2*maxlines, 100)
try:
while True:
for x in xrange(lines2read):
out.append(F.next())
out = out[-maxlines:]
except StopIteration:
pass
return out[-maxlines:]

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