# Copyright (c) Open-MMLab. All rights reserved.
import functools
import itertools
import subprocess
from collections import abc
from importlib import import_module
[docs]def is_str(x):
"""Whether the input is an string instance.
Note: This method is deprecated since python 2 is no longer supported.
"""
return isinstance(x, str)
[docs]def iter_cast(inputs, dst_type, return_type=None):
"""Cast elements of an iterable object into some type.
Args:
inputs (Iterable): The input object.
dst_type (type): Destination type.
return_type (type, optional): If specified, the output object will be
converted to this type, otherwise an iterator.
Returns:
iterator or specified type: The converted object.
"""
if not isinstance(inputs, abc.Iterable):
raise TypeError('inputs must be an iterable object')
if not isinstance(dst_type, type):
raise TypeError('"dst_type" must be a valid type')
out_iterable = map(dst_type, inputs)
if return_type is None:
return out_iterable
else:
return return_type(out_iterable)
[docs]def list_cast(inputs, dst_type):
"""Cast elements of an iterable object into a list of some type.
A partial method of :func:`iter_cast`.
"""
return iter_cast(inputs, dst_type, return_type=list)
[docs]def tuple_cast(inputs, dst_type):
"""Cast elements of an iterable object into a tuple of some type.
A partial method of :func:`iter_cast`.
"""
return iter_cast(inputs, dst_type, return_type=tuple)
[docs]def is_seq_of(seq, expected_type, seq_type=None):
"""Check whether it is a sequence of some type.
Args:
seq (Sequence): The sequence to be checked.
expected_type (type): Expected type of sequence items.
seq_type (type, optional): Expected sequence type.
Returns:
bool: Whether the sequence is valid.
"""
if seq_type is None:
exp_seq_type = abc.Sequence
else:
assert isinstance(seq_type, type)
exp_seq_type = seq_type
if not isinstance(seq, exp_seq_type):
return False
for item in seq:
if not isinstance(item, expected_type):
return False
return True
[docs]def is_list_of(seq, expected_type):
"""Check whether it is a list of some type.
A partial method of :func:`is_seq_of`.
"""
return is_seq_of(seq, expected_type, seq_type=list)
[docs]def is_tuple_of(seq, expected_type):
"""Check whether it is a tuple of some type.
A partial method of :func:`is_seq_of`.
"""
return is_seq_of(seq, expected_type, seq_type=tuple)
[docs]def slice_list(in_list, lens):
"""Slice a list into several sub lists by a list of given length.
Args:
in_list (list): The list to be sliced.
lens(int or list): The expected length of each out list.
Returns:
list: A list of sliced list.
"""
if isinstance(lens, int):
assert len(in_list) % lens == 0
lens = [lens] * int(len(in_list) / lens)
if not isinstance(lens, list):
raise TypeError('"indices" must be an integer or a list of integers')
elif sum(lens) != len(in_list):
raise ValueError(
'sum of lens and list length does not match: {} != {}'.format(
sum(lens), len(in_list)))
out_list = []
idx = 0
for i in range(len(lens)):
out_list.append(in_list[idx:idx + lens[i]])
idx += lens[i]
return out_list
[docs]def concat_list(in_list):
"""Concatenate a list of list into a single list.
Args:
in_list (list): The list of list to be merged.
Returns:
list: The concatenated flat list.
"""
return list(itertools.chain(*in_list))
[docs]def check_prerequisites(
prerequisites,
checker,
msg_tmpl='Prerequisites "{}" are required in method "{}" but not '
'found, please install them first.'): # yapf: disable
"""A decorator factory to check if prerequisites are satisfied.
Args:
prerequisites (str of list[str]): Prerequisites to be checked.
checker (callable): The checker method that returns True if a
prerequisite is meet, False otherwise.
msg_tmpl (str): The message template with two variables.
Returns:
decorator: A specific decorator.
"""
def wrap(func):
@functools.wraps(func)
def wrapped_func(*args, **kwargs):
requirements = [prerequisites] if isinstance(
prerequisites, str) else prerequisites
missing = []
for item in requirements:
if not checker(item):
missing.append(item)
if missing:
print(msg_tmpl.format(', '.join(missing), func.__name__))
raise RuntimeError('Prerequisites not meet.')
else:
return func(*args, **kwargs)
return wrapped_func
return wrap
def _check_py_package(package):
try:
import_module(package)
except ImportError:
return False
else:
return True
def _check_executable(cmd):
if subprocess.call('which {}'.format(cmd), shell=True) != 0:
return False
else:
return True
[docs]def requires_package(prerequisites):
"""A decorator to check if some python packages are installed.
Example:
>>> @requires_package('numpy')
>>> func(arg1, args):
>>> return numpy.zeros(1)
array([0.])
>>> @requires_package(['numpy', 'non_package'])
>>> func(arg1, args):
>>> return numpy.zeros(1)
ImportError
"""
return check_prerequisites(prerequisites, checker=_check_py_package)
[docs]def requires_executable(prerequisites):
"""A decorator to check if some executable files are installed.
Example:
>>> @requires_executable('ffmpeg')
>>> func(arg1, args):
>>> print(1)
1
"""
return check_prerequisites(prerequisites, checker=_check_executable)