read(n) 与 mock_open 兼容吗？

Question

[更新：这是a known bug。]

有没有办法将 read(some_number_of_bytes) 与 mock_open 一起使用？

mock_open 在读取整个文件 (read()) 或读取单行 (readline()) 时按预期工作，但在读取文件时无法正常工作字节数 (read(n))

这些片段（改编自 Mock documentation）适用于 (Python 2.7)：

from mock import mock_open, patch

# works: consume entire "file"
with patch('__main__.open', mock_open(read_data='bibble')) as m:
    with open('foo') as h:
        result = h.read()

assert result == 'bibble'  # ok

# works: consume one line
with patch('__main__.open', mock_open(read_data='bibble\nbobble')) as m:
    with open('foo') as h:
        result = h.readline()

assert result == 'bibble\n'  # ok

但是尝试只读取几个字节失败--mock_open returns 整个 read_data 相反：

# consume first 3 bytes of the "file"
with patch('__main__.open', mock_open(read_data='bibble')) as m:
    with open('foo') as h:
        result = h.read(3)

assert result == 'bib', 'result of read: {}'.format(result)  # fails

输出：

Traceback (most recent call last):
  File "/tmp/t.py", line 25, in <module>
    assert result == 'bib', 'result of read: {}'.format(result)
AssertionError: result of read: bibble

如果这是一个 XY 问题，我会注意到这个问题的原因是我正在模拟我传递给 pickle.load 的文件，该文件又调用 read(1) .

with open('/path/to/file.pkl', 'rb') as f:
    x = pickle.load(f)  # this requires f.read(1) to work

我更愿意模拟尽可能低的级别（open 而不是 pickle.load）。

Answer 1

郑重声明，本期has been fixed in Python 3.7。

read(n) 与 mock_open 兼容吗？

Is read(n) compatible with mock_open?

python

python-mock