Python 3.6+递归文件夹/文件大小使用os.scandir。和@blakev的回答一样强大，但更短，采用EAFP python风格。

import os

def size(path, *, follow_symlinks=False):
    try:
        with os.scandir(path) as it:
            return sum(size(entry, follow_symlinks=follow_symlinks) for entry in it)
    except NotADirectoryError:
        return os.stat(path, follow_symlinks=follow_symlinks).st_size

Chris的回答很好，但可以通过使用set来检查已看到的目录来使其更加惯用，这也避免了对控制流使用异常:

def directory_size(path):
    total_size = 0
    seen = set()

    for dirpath, dirnames, filenames in os.walk(path):
        for f in filenames:
            fp = os.path.join(dirpath, f)

            try:
                stat = os.stat(fp)
            except OSError:
                continue

            if stat.st_ino in seen:
                continue

            seen.add(stat.st_ino)

            total_size += stat.st_size

    return total_size  # size in bytes

这是一个递归地完成它的一行代码(从Python 3.5开始提供递归选项):

import os
import glob
print(sum(os.path.getsize(f) for f in glob.glob('**', recursive=True) if os.path.isfile(f))/(1024*1024))

这将遍历所有子目录;文件大小总和:

import os

def get_size(start_path = '.'):
    total_size = 0
    for dirpath, dirnames, filenames in os.walk(start_path):
        for f in filenames:
            fp = os.path.join(dirpath, f)
            # skip if it is symbolic link
            if not os.path.islink(fp):
                total_size += os.path.getsize(fp)

    return total_size

print(get_size(), 'bytes')

和一个在线的乐趣使用操作系统。listdir(不包括子目录):

import os
sum(os.path.getsize(f) for f in os.listdir('.') if os.path.isfile(f))

参考:

os.path.getsize -以字节为单位给出大小 os.walk os.path.islink

更新 使用os.path。Getsize，这比使用os.stat()更清楚。st_size方法。

感谢ghostdog74指出这一点!

操作系统。stat - st_size以字节为单位给出大小。也可用于获取文件大小等文件相关信息。

import os

nbytes = sum(d.stat().st_size for d in os.scandir('.') if d.is_file())

更新2018

如果您使用的是Python 3.4或更早版本，那么您可以考虑使用第三方scandir包提供的更有效的walk方法。在Python 3.5及以后版本中，此包已合并到标准库和操作系统中。行走得到了相应的性能提升。

更新2019

最近我越来越多地使用pathlib，这里有一个pathlib解决方案:

from pathlib import Path

root_directory = Path('.')
sum(f.stat().st_size for f in root_directory.glob('**/*') if f.is_file())

下面的脚本打印指定目录的所有子目录的目录大小。它还试图(如果可能的话)从缓存递归函数的调用中获益。如果省略一个参数，脚本将在当前目录中工作。输出按目录大小从大到小排序。所以你可以根据自己的需要进行调整。

PS我已经使用配方578019以人性化的格式显示目录大小(http://code.activestate.com/recipes/578019/)

from __future__ import print_function
import os
import sys
import operator

def null_decorator(ob):
    return ob

if sys.version_info >= (3,2,0):
    import functools
    my_cache_decorator = functools.lru_cache(maxsize=4096)
else:
    my_cache_decorator = null_decorator

start_dir = os.path.normpath(os.path.abspath(sys.argv[1])) if len(sys.argv) > 1 else '.'

@my_cache_decorator
def get_dir_size(start_path = '.'):
    total_size = 0
    if 'scandir' in dir(os):
        # using fast 'os.scandir' method (new in version 3.5)
        for entry in os.scandir(start_path):
            if entry.is_dir(follow_symlinks = False):
                total_size += get_dir_size(entry.path)
            elif entry.is_file(follow_symlinks = False):
                total_size += entry.stat().st_size
    else:
        # using slow, but compatible 'os.listdir' method
        for entry in os.listdir(start_path):
            full_path = os.path.abspath(os.path.join(start_path, entry))
            if os.path.isdir(full_path):
                total_size += get_dir_size(full_path)
            elif os.path.isfile(full_path):
                total_size += os.path.getsize(full_path)
    return total_size

def get_dir_size_walk(start_path = '.'):
    total_size = 0
    for dirpath, dirnames, filenames in os.walk(start_path):
        for f in filenames:
            fp = os.path.join(dirpath, f)
            total_size += os.path.getsize(fp)
    return total_size

def bytes2human(n, format='%(value).0f%(symbol)s', symbols='customary'):
    """
    (c) http://code.activestate.com/recipes/578019/

    Convert n bytes into a human readable string based on format.
    symbols can be either "customary", "customary_ext", "iec" or "iec_ext",
    see: http://goo.gl/kTQMs

      >>> bytes2human(0)
      '0.0 B'
      >>> bytes2human(0.9)
      '0.0 B'
      >>> bytes2human(1)
      '1.0 B'
      >>> bytes2human(1.9)
      '1.0 B'
      >>> bytes2human(1024)
      '1.0 K'
      >>> bytes2human(1048576)
      '1.0 M'
      >>> bytes2human(1099511627776127398123789121)
      '909.5 Y'

      >>> bytes2human(9856, symbols="customary")
      '9.6 K'
      >>> bytes2human(9856, symbols="customary_ext")
      '9.6 kilo'
      >>> bytes2human(9856, symbols="iec")
      '9.6 Ki'
      >>> bytes2human(9856, symbols="iec_ext")
      '9.6 kibi'

      >>> bytes2human(10000, "%(value).1f %(symbol)s/sec")
      '9.8 K/sec'

      >>> # precision can be adjusted by playing with %f operator
      >>> bytes2human(10000, format="%(value).5f %(symbol)s")
      '9.76562 K'
    """
    SYMBOLS = {
        'customary'     : ('B', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'),
        'customary_ext' : ('byte', 'kilo', 'mega', 'giga', 'tera', 'peta', 'exa',
                           'zetta', 'iotta'),
        'iec'           : ('Bi', 'Ki', 'Mi', 'Gi', 'Ti', 'Pi', 'Ei', 'Zi', 'Yi'),
        'iec_ext'       : ('byte', 'kibi', 'mebi', 'gibi', 'tebi', 'pebi', 'exbi',
                           'zebi', 'yobi'),
    }
    n = int(n)
    if n < 0:
        raise ValueError("n < 0")
    symbols = SYMBOLS[symbols]
    prefix = {}
    for i, s in enumerate(symbols[1:]):
        prefix[s] = 1 << (i+1)*10
    for symbol in reversed(symbols[1:]):
        if n >= prefix[symbol]:
            value = float(n) / prefix[symbol]
            return format % locals()
    return format % dict(symbol=symbols[0], value=n)

############################################################
###
###  main ()
###
############################################################
if __name__ == '__main__':
    dir_tree = {}
    ### version, that uses 'slow' [os.walk method]
    #get_size = get_dir_size_walk
    ### this recursive version can benefit from caching the function calls (functools.lru_cache)
    get_size = get_dir_size

    for root, dirs, files in os.walk(start_dir):
        for d in dirs:
            dir_path = os.path.join(root, d)
            if os.path.isdir(dir_path):
                dir_tree[dir_path] = get_size(dir_path)

    for d, size in sorted(dir_tree.items(), key=operator.itemgetter(1), reverse=True):
        print('%s\t%s' %(bytes2human(size, format='%(value).2f%(symbol)s'), d))

    print('-' * 80)
    if sys.version_info >= (3,2,0):
        print(get_dir_size.cache_info())

样例输出:

37.61M  .\subdir_b
2.18M   .\subdir_a
2.17M   .\subdir_a\subdir_a_2
4.41K   .\subdir_a\subdir_a_1
----------------------------------------------------------
CacheInfo(hits=2, misses=4, maxsize=4096, currsize=4)

编辑:根据user2233949的建议，将null_decorator移到上面

Du默认情况下不遵循符号链接。这里没有答案，使用follow_symlinks=False。

下面是一个遵循du默认行为的实现:

def du(path) -> int:
    total = 0
    for entry in os.scandir(path):
        if entry.is_file(follow_symlinks=False):
            total += entry.stat().st_size
        elif entry.is_dir(follow_symlinks=False):
            total += du(entry.path)
    return total

测试:

class Test(unittest.TestCase):
    def test_du(self):
        root = '/tmp/du_test'
        subprocess.run(['rm', '-rf', root])
        test_utils.mkdir(root)
        test_utils.create_file(root, 'A', '1M')
        test_utils.create_file(root, 'B', '1M')
        sub = '/'.join([root, 'sub'])
        test_utils.mkdir(sub)
        test_utils.create_file(sub, 'C', '1M')
        test_utils.create_file(sub, 'D', '1M')
        subprocess.run(['ln', '-s', '/tmp', '/'.join([root, 'link']), ])
        self.assertEqual(4 << 20, util.du(root))