Pickle 没有将数据保存到具有格式化字符串名称的文件中

Question

I am baffled by the behavior of the code below. There are two problems; I am not sure whether they are related in some strange way.

The first problem is the more important one. The code should save two files containing the same data. However, test.pkl is about 79 kB whereas the other is empty. Why is nothing being saved there after the file is created?

The second issue I noticed is that the second file is saved as something like ev-w1-n2-2020-12-13-19 without any file extension. What happened to the .pkl ?

I am using Python 3.8 with pickle 4.0 on Windows 10.

import pickle
import numpy as np
import datetime

n = 100
z = np.zeros((n,n))
with open("test.pkl" , 'wb') as myfile:
    pickle.dump(z, myfile)

filename = "e-v-w%s-n%s-%s.pkl" % (1, 2, datetime.datetime.now().strftime("%Y-%m-%d-%H:%M"))
print(filename)
with open(filename, "wb") as outfile:
    pickle.dump(z, outfile, pickle.HIGHEST_PROTOCOL)

When I print filename , the .pkl appears as it should, by the way.

Answer 1

The colon character (":") is not allowed in Windows filepaths, for example this post .

Your strftime format includes a colon, which makes it impossible for that path to be written to, and is also presumably the reason why the characters after the colon (suck as the .pkl extension) are missing.

Running your code on a Unix platform worked as expected. Simply change your strftime format to make it compatible with Windows.