Shelve Data Storage

#Source: https://docs.python.org/3/library/shelve.html
import shelve

d = shelve.open(filename)  # open -- file may get suffix added by low-level
                           # library

d[key] = data              # store data at key (overwrites old data if
                           # using an existing key)
data = d[key]              # retrieve a COPY of data at key (raise KeyError
                           # if no such key)
del d[key]                 # delete data stored at key (raises KeyError
                           # if no such key)

flag = key in d            # true if the key exists
klist = list(d.keys())     # a list of all existing keys (slow!)

# as d was opened WITHOUT writeback=True, beware:
d['xx'] = [0, 1, 2]        # this works as expected, but...
d['xx'].append(3)          # *this doesn't!* -- d['xx'] is STILL [0, 1, 2]!

# having opened d without writeback=True, you need to code carefully:
temp = d['xx']             # extracts the copy
temp.append(5)             # mutates the copy
d['xx'] = temp             # stores the copy right back, to persist it

# or, d=shelve.open(filename,writeback=True) would let you just code
# d['xx'].append(5) and have it work as expected, BUT it would also
# consume more memory and make the d.close() operation slower.

d.close()                  # close it

Source: docs.python.org

Similar codes

1 vote145 views4 answers
Flask activ environment
Python
0 vote142 views1 answer
Pandas typr of each cell in series
Python
2 votes128 views1 answer
Fstring number format python
Python
-1 vote205 views2 answers
Django forms error customize
Python Django
0 vote133 views1 answer
Sudo in python
Python
-1 vote129 views1 answer
How to normalize a 1d numpy array
Python
0 vote335 views1 answer
Get sum of column before a date python
Python
0 vote137 views1 answer
Programmer tool
Python
0 vote127 views1 answer
Is there a way to refer back to a previous line in python
Python
0 vote133 views1 answer
List comprehension python one line
Python