python - 对 python 方法中的 self 参数感到困惑(不属于任何类的方法)

Question

我正在尝试阅读一些 github 代码，以便能够修改它以满足我的需要。我正在努力理解 this file .它不包含任何 class 关键字，但在方法定义中使用 self 关键字。我想我的问题是方法声明中的那些 self 指的是什么？另一个相关问题是这个文件是什么(即它是否起作用)？

任何评论、建议、指示都会有很大帮助。谢谢!

下面是我在链接中引用的代码:

"""
tfnet secondary (helper) methods
"""
from ..utils.loader import create_loader
from time import time as timer
import tensorflow as tf
import numpy as np
import sys
import cv2
import os
import csv

old_graph_msg = 'Resolving old graph def {} (no guarantee)'

def build_train_op(self):
    self.framework.loss(self.out)
    self.say('Building {} train op'.format(self.meta['model']))
    optimizer = self._TRAINER[self.FLAGS.trainer](self.FLAGS.lr)
    gradients = optimizer.compute_gradients(self.framework.loss)
    self.train_op = optimizer.apply_gradients(gradients)

def load_from_ckpt(self):
    if self.FLAGS.load < 0: # load lastest ckpt
        with open(self.FLAGS.backup + 'checkpoint', 'r') as f:
            last = f.readlines()[-1].strip()
            load_point = last.split(' ')[1]
            load_point = load_point.split('"')[1]
            load_point = load_point.split('-')[-1]
            self.FLAGS.load = int(load_point)

    load_point = os.path.join(self.FLAGS.backup, self.meta['name'])
    load_point = '{}-{}'.format(load_point, self.FLAGS.load)
    self.say('Loading from {}'.format(load_point))
    try: self.saver.restore(self.sess, load_point)
    except: load_old_graph(self, load_point)

def say(self, *msgs):
    if not self.FLAGS.verbalise:
        return
    msgs = list(msgs)
    for msg in msgs:
        if msg is None: continue
        print(msg)

def load_old_graph(self, ckpt):
    ckpt_loader = create_loader(ckpt)
    self.say(old_graph_msg.format(ckpt))

    for var in tf.global_variables():
        name = var.name.split(':')[0]
        args = [name, var.get_shape()]
        val = ckpt_loader(args)
        assert val is not None, \
        'Cannot find and load {}'.format(var.name)
        shp = val.shape
        plh = tf.placeholder(tf.float32, shp)
        op = tf.assign(var, plh)
        self.sess.run(op, {plh: val})

def _get_fps(self, frame):
    elapsed = int()
    start = timer()
    preprocessed = self.framework.preprocess(frame)
    feed_dict = {self.inp: [preprocessed]}
    net_out = self.sess.run(self.out, feed_dict)[0]
    processed = self.framework.postprocess(net_out, frame, False)
    return timer() - start

def camera(self):
    file = self.FLAGS.demo
    SaveVideo = self.FLAGS.saveVideo

    if self.FLAGS.track :
        if self.FLAGS.tracker == "deep_sort":
            from deep_sort import generate_detections
            from deep_sort.deep_sort import nn_matching
            from deep_sort.deep_sort.tracker import Tracker
            metric = nn_matching.NearestNeighborDistanceMetric(
            "cosine", 0.2, 100)
            tracker = Tracker(metric)
            encoder = generate_detections.create_box_encoder(
                os.path.abspath("deep_sort/resources/networks/mars-small128.ckpt-68577"))
        elif self.FLAGS.tracker == "sort":
            from sort.sort import Sort
            encoder = None
            tracker = Sort()
    if self.FLAGS.BK_MOG and self.FLAGS.track :
        fgbg = cv2.bgsegm.createBackgroundSubtractorMOG()

    if file == 'camera':
        file = 0
    else:
        assert os.path.isfile(file), \
        'file {} does not exist'.format(file)

    camera = cv2.VideoCapture(file)

    if file == 0:
        self.say('Press [ESC] to quit video')

    assert camera.isOpened(), \
    'Cannot capture source'

    if self.FLAGS.csv :
        f = open('{}.csv'.format(file),'w')
        writer = csv.writer(f, delimiter=',')
        writer.writerow(['frame_id', 'track_id' , 'x', 'y', 'w', 'h'])
        f.flush()
    else :
        f =None
        writer= None
    if file == 0:#camera window
        cv2.namedWindow('', 0)
        _, frame = camera.read()
        height, width, _ = frame.shape
        cv2.resizeWindow('', width, height)
    else:
        _, frame = camera.read()
        height, width, _ = frame.shape

    if SaveVideo:
        fourcc = cv2.VideoWriter_fourcc(*'XVID')
        if file == 0:#camera window
          fps = 1 / self._get_fps(frame)
          if fps < 1:
            fps = 1
        else:
            fps = round(camera.get(cv2.CAP_PROP_FPS))
        videoWriter = cv2.VideoWriter(
            'output_{}'.format(file), fourcc, fps, (width, height))

    # buffers for demo in batch
    buffer_inp = list()
    buffer_pre = list()

    elapsed = 0
    start = timer()
    self.say('Press [ESC] to quit demo')
    #postprocessed = []
    # Loop through frames
    n = 0
    while camera.isOpened():
        elapsed += 1
        _, frame = camera.read()
        if frame is None:
            print ('\nEnd of Video')
            break
        if self.FLAGS.skip != n :
            n+=1
            continue
        n = 0
        if self.FLAGS.BK_MOG and self.FLAGS.track :
            fgmask = fgbg.apply(frame)
        else :
            fgmask = None
        preprocessed = self.framework.preprocess(frame)
        buffer_inp.append(frame)
        buffer_pre.append(preprocessed)
        # Only process and imshow when queue is full
        if elapsed % self.FLAGS.queue == 0:
            feed_dict = {self.inp: buffer_pre}
            net_out = self.sess.run(self.out, feed_dict)
            for img, single_out in zip(buffer_inp, net_out):
                if not self.FLAGS.track :
                    postprocessed = self.framework.postprocess(
                        single_out, img, save= False)
                else :
                    postprocessed = self.framework.postprocess(
                        single_out, img,frame_id = elapsed,csv_file=f,csv=writer,mask = fgmask,encoder=encoder,tracker=tracker,save=False)
                if SaveVideo:
                    videoWriter.write(postprocessed)
                if self.FLAGS.display :
                    cv2.imshow('', postprocessed)
            # Clear Buffers
            buffer_inp = list()
            buffer_pre = list()

        if elapsed % 5 == 0:
            sys.stdout.write('\r')
            sys.stdout.write('{0:3.3f} FPS'.format(
                elapsed / (timer() - start)))
            sys.stdout.flush()
        if self.FLAGS.display :
            choice = cv2.waitKey(1)
            if choice == 27:
                break

    sys.stdout.write('\n')
    if SaveVideo:
        videoWriter.release()
    if self.FLAGS.csv :
        f.close()
    camera.release()
    if self.FLAGS.display :
        cv2.destroyAllWindows()

def to_darknet(self):
    darknet_ckpt = self.darknet

    with self.graph.as_default() as g:
        for var in tf.global_variables():
            name = var.name.split(':')[0]
            var_name = name.split('-')
            l_idx = int(var_name[0])
            w_sig = var_name[1].split('/')[-1]
            l = darknet_ckpt.layers[l_idx]
            l.w[w_sig] = var.eval(self.sess)

    for layer in darknet_ckpt.layers:
        for ph in layer.h:
            layer.h[ph] = None

    return darknet_ckpt

Answer 1

这是一个相当复杂的设置。基本上，help.py 文件中“独立”的函数随后被“修补”到其他类定义中(参见 build.py ...

from . import help
...    
class TFNet(object):
    ...
    # imported methods
    say = help.say
    load_from_ckpt = help.load_from_ckpt
    ...
            self.say('\nLoading from .pb and .meta')
    ...    
        if self.FLAGS.load != 0: self.load_from_ckpt()

在函数定义中不包含任何文档字符串来解释参数是什么真的很糟糕(imo)。

做这种事情的更正常的方法是让父类可以被派生类继承。

编辑以回答您在评论中的问题，是的。像这样

import help

class OddSystem(object):
  say = help.say

o = OddSystem()
o.say('hello world!')

# more normal system would use inheritance, help.py defines a parent class Help
class NormalSystem(help.Help):
  def __init__(self):
    ''' normal definitions etc '''
    pass

n = NormalSystem()
n.say('that is better!')

help.py 是同一目录下的文件:

def say(self, msg):
  print(msg)

class Help(object):
  def say(self, msg):
    print(msg)