Examples of using the Python LMDB library

pip install lmdb

# -*- coding: utf-8 -*-
import lmdb
# If there is no or file in the train folder, an empty one will be generated, if there is, it will not be overwritten
# map_size defines the maximum storage capacity in kilobytes (kb), the following defines 1TB capacity
env = ("./train"，map_size=1099511627776)
()

# -*- coding: utf-8 -*-
import lmdb
# map_size defines the maximum storage capacity in kilobytes (kb), the following defines 1TB capacity
env = ("./train", map_size=1099511627776)
txn = (write=True)

# Add data and keys
(key = '1', value = 'aaa')
(key = '2', value = 'bbb')
(key = '3', value = 'ccc')
 
# Delete data by key value
(key = '1')
 
# Modify data
(key = '3', value = 'ddd')
 
# Commit changes via the commit() function
()
()

# -*- coding: utf-8 -*-
import lmdb
 
env = ("./train")
 
# The parameter write is set to True to write.
txn = (write=True)
############################################ add, modify, delete data
 
# Add data and keys
(key = '1', value = 'aaa')
(key = '2', value = 'bbb')
(key = '3', value = 'ccc')
 
# Delete data by key value
(key = '1')
 
# Modify data
(key = '3', value = 'ddd')
 
# Commit changes via the commit() function
()
############################################ query lmdb data
txn = ()
 
# get function queries data by key value
print (str(2))
 
# Iterate over all data and keys with cursor()
for key, value in ():
  print (key, value)
  
############################################
()

# -*- coding: utf-8 -*-
import lmdb
 
env_db = ('trainC')
# env_db = ("./trainC")
 
txn = env_db.begin()
 
# get function queries the data by key value, if the key value to be queried does not have corresponding data, then output None
print (str(200))
 
for key, value in (): # traversing
  print (key, value)
 
env_db.close()