在python中使用pickle存储字典

Question

我编写了这段代码，用于计算pdf文件的哈希值，并将其添加到字典中，然后将其保存到这样的文件中：

v={hash_value:{"file name":file_name,"number":1}}

但是以下代码的问题是，如果我添加一个新文件，它将覆盖前一个文件。

f = calculate_hash("calc.pdf")
v = {f:{"file name":"calc.pdf","number":1}}

with open('filename.pickle', 'wb') as handle:
    pickle.dump(v, handle)  

with open('filename.pickle', 'rb') as handle:
    b = pickle.load(handle)

x=  calculate_hash("calc.pdf")
for key in b:
    print key
    if x == key:
        print "yes"

Answer 1

只需使用“追加”模式即可：

with open('filename.pickle', 'wb') as handle:

=>

with open('filename.pickle', 'ab') as handle:

Answer 2

打开文件时，需要使用“ a”代替“ w”。

查看读写文件

Answer 3

这里的主要错误是您在读取文件之前先将其写入。 从而覆盖所有现有值，而不是将现有值与新值组合。

这个怎么样？

import pickle
import random

def calculate_hash(s):
    return random.randint(1, 100) # not proper hash

f = calculate_hash("calc.pdf")
v = {f:{"file name":"calc.pdf","number":1}}

# read before you write
with open('filename.pickle', 'rb') as handle: # file has to exist here
    b = pickle.load(handle)

# combine the two dictionaries
b = dict(b.items() + v.items())

# write the combined dictionaries
with open('filename.pickle', 'wb') as handle:
    pickle.dump(b, handle)  

x=  calculate_hash("calc.pdf")
for key in b:
    print key
    if x == key:
        print "yes"