python文件排序的方法总结

在python环境中提供两种排序方案：用库函数sorted()对字符串排序，它的对象是字符；用函数sort()对数字排序，它的对象是数字，如果读取文件的话，需要进行处理（把文件后缀名‘屏蔽’）。

（1）首先：我测试的文件夹是/img/，里面的文件都是图片，如下图所示：

（2）测试库函数sorted()，直接贴出代码：

import numpy as npimport os img_path=’./img/’ img_list=sorted(os.listdir(img_path))#文件名按字母排序img_nums=len(img_list)for i in range(img_nums): img_name=img_path+img_list[i] print(img_name)

运行效果如下：

从图片可以清晰的看出，文件名是按字符排序的。

（3）测试函数sort()，代码：

import numpy as npimport osimg_path=’./img/’ img_list=os.listdir(img_path)img_list.sort()img_list.sort(key = lambda x: int(x[:-4])) ##文件名按数字排序img_nums=len(img_list)for i in range(img_nums): img_name=img_path+img_list[i] print(img_name)

运行效果如下：

可以看出，文件名是按数字排序的；顺便提下，sort函数中用到了匿名函数(key = lambda x:int(x[:-4]))，其作用是将后缀名’.jpg’“屏蔽”（因为‘.jpg’是4个字符，所以[:-4]的含义是从文件名开始到倒数第四个字符为止），具体看python的匿名函数和数组取值方式。

实例扩展：

import gzipimport osfrom multiprocessing import Process, Queue, Pipe, current_process, freeze_supportfrom datetime import datetimedef sort_worker(input,output): while True: lines = input.get().splitlines() element_set = {} for line in lines: if line.strip() == ’STOP’: return try: element = line.split(’ ’)[0] if not element_set.get(element): element_set[element] = ’’ except: pass sorted_element = sorted(element_set) #print sorted_element output.put(’n’.join(sorted_element))def write_worker(input, pre): os.system(’mkdir %s’%pre) i = 0 while True: content = input.get() if content.strip() == ’STOP’: return write_sorted_bulk(content, ’%s/%s’%(pre, i)) i += 1def write_sorted_bulk(content, filename): f = file(filename, ’w’) f.write(content) f.close()def split_sort_file(filename, num_sort = 3, buf_size = 65536*64*4): t = datetime.now() pre, ext = os.path.splitext(filename) if ext == ’.gz’: file_file = gzip.open(filename, ’rb’) else: file_file = open(filename) bulk_queue = Queue(10) sorted_queue = Queue(10) NUM_SORT = num_sort sort_worker_pool = [] for i in range(NUM_SORT): sort_worker_pool.append( Process(target=sort_worker, args=(bulk_queue, sorted_queue)) ) sort_worker_pool[i].start() NUM_WRITE = 1 write_worker_pool = [] for i in range(NUM_WRITE): write_worker_pool.append( Process(target=write_worker, args=(sorted_queue, pre)) ) write_worker_pool[i].start() buf = file_file.read(buf_size) sorted_count = 0 while len(buf): end_line = buf.rfind(’n’) #print buf[:end_line+1] bulk_queue.put(buf[:end_line+1]) sorted_count += 1 if end_line != -1: buf = buf[end_line+1:] + file_file.read(buf_size) else: buf = file_file.read(buf_size) for i in range(NUM_SORT): bulk_queue.put(’STOP’) for i in range(NUM_SORT): sort_worker_pool[i].join() for i in range(NUM_WRITE): sorted_queue.put(’STOP’) for i in range(NUM_WRITE): write_worker_pool[i].join() print ’elasped ’, datetime.now() - t return sorted_countfrom heapq import heappush, heappopfrom datetime import datetimefrom multiprocessing import Process, Queue, Pipe, current_process, freeze_supportimport osclass file_heap: def __init__(self, dir, idx = 0, count = 1): files = os.listdir(dir) self.heap = [] self.files = {} self.bulks = {} self.pre_element = None for i in range(len(files)): file = files[i] if hash(file) % count != idx: continue input = open(os.path.join(dir, file)) self.files[i] = input self.bulks[i] = ’’ heappush(self.heap, (self.get_next_element_buffered(i), i)) def get_next_element_buffered(self, i): if len(self.bulks[i]) < 256: if self.files[i] is not None: buf = self.files[i].read(65536) if buf: self.bulks[i] += buf else: self.files[i].close() self.files[i] = None end_line = self.bulks[i].find(’n’) if end_line == -1: end_line = len(self.bulks[i]) element = self.bulks[i][:end_line] self.bulks[i] = self.bulks[i][end_line+1:] return element def poppush_uniq(self): while True: element = self.poppush() if element is None: return None if element != self.pre_element: self.pre_element = element return element def poppush(self): try: element, index = heappop(self.heap) except IndexError: return None new_element = self.get_next_element_buffered(index) if new_element: heappush(self.heap, (new_element, index)) return elementdef heappoppush(dir, queue, idx = 0, count = 1): heap = file_heap(dir, idx, count) while True: d = heap.poppush_uniq() queue.put(d) if d is None: returndef heappoppush2(dir, queue, count = 1): heap = [] procs = [] queues = [] pre_element = None for i in range(count): q = Queue(1024) q_buf = queue_buffer(q) queues.append(q_buf) p = Process(target=heappoppush, args=(dir, q_buf, i, count)) procs.append(p) p.start() queues = tuple(queues) for i in range(count): heappush(heap, (queues[i].get(), i)) while True: try: d, i= heappop(heap) except IndexError: queue.put(None) for p in procs: p.join() return else: if d is not None: heappush(heap,(queues[i].get(), i)) if d != pre_element: pre_element = d queue.put(d)def merge_file(dir): heap = file_heap( dir ) os.system(’rm -f ’+dir+’.merge’) fmerge = open(dir+’.merge’, ’a’) element = heap.poppush_uniq() fmerge.write(element+’n’) while element is not None: element = heap.poppush_uniq() fmerge.write(element+’n’)class queue_buffer: def __init__(self, queue): self.q = queue self.rbuf = [] self.wbuf = [] def get(self): if len(self.rbuf) == 0: self.rbuf = self.q.get() r = self.rbuf[0] del self.rbuf[0] return r def put(self, d): self.wbuf.append(d) if d is None or len(self.wbuf) > 1024: self.q.put(self.wbuf) self.wbuf = []def diff_file(file_old, file_new, file_diff, buf = 268435456): print ’buffer size’, buf from file_split import split_sort_file os.system(’rm -rf ’+ os.path.splitext(file_old)[0] ) os.system(’rm -rf ’+ os.path.splitext(file_new)[0] ) t = datetime.now() split_sort_file(file_old,5,buf) split_sort_file(file_new,5,buf) print ’split elasped ’, datetime.now() - t os.system(’cat %s/* | wc -l’%os.path.splitext(file_old)[0]) os.system(’cat %s/* | wc -l’%os.path.splitext(file_new)[0]) os.system(’rm -f ’+file_diff) t = datetime.now() zdiff = open(file_diff, ’a’) old_q = Queue(1024) new_q = Queue(1024) old_queue = queue_buffer(old_q) new_queue = queue_buffer(new_q) h1 = Process(target=heappoppush2, args=(os.path.splitext(file_old)[0], old_queue, 3)) h2 = Process(target=heappoppush2, args=(os.path.splitext(file_new)[0], new_queue, 3)) h1.start(), h2.start() old = old_queue.get() new = new_queue.get() old_count, new_count = 0, 0 while old is not None or new is not None: if old > new or old is None: zdiff.write(’< ’+new+’n’) new = new_queue.get() new_count +=1 elif old < new or new is None: zdiff.write(’> ’+old+’n’) old = old_queue.get() old_count +=1 else: old = old_queue.get() new = new_queue.get() print ’new_count:’, new_count print ’old_count:’, old_count print ’diff elasped ’, datetime.now() - t h1.join(), h2.join()

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