# Copyright 2022 Cerebras Systems.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from glob import glob
from itertools import repeat, takewhile
[docs]def count_lines(filename_pattern):
"""
Returns linecount in the given filename or sum over all of
the filenames matching the pattern.
Takes a filename pattern and globs the pattern
to get all matching filenames. In order, this function reads all the
files in raw format for a fixed buffer size till EOF is reached. It
then counts the number of ``\n``
in each buffer and returns the sum. Using ``takewhile`` and ``repeat``
provides inbuilt speedup compared to writing custom while/for loop to
handle EOF.
`Note`: The size of the buffer is currently set to 1024*1024, but this
is not optimized for all files. Some files can be read in faster by
modifying the buffer size. This value is suboptimal to memory usage on
a local dev instance.
:param str filename_pattern: filename glob pattern (or filename)
:returns: integer number of lines in the file
"""
line_count = 0
for filename in glob(filename_pattern):
with open(filename, "rb") as f:
bufgen = takewhile(
lambda x: x, (f.raw.read(1024 * 1024) for _ in repeat(None))
)
line_count += sum(buf.count(b'\n') for buf in bufgen)
# check if last line has "\n"; if not increment line count by 1
with open(filename, "r") as f:
# seek to the end of the file
f.seek(0, 2)
# seek the last character of file
f.seek(f.tell() - 1, 0)
if f.read() != "\n":
line_count += 1
return line_count