Python Shelve eg2....- Day 13

updating shelve

  
import shelve
# with shelve.open("D:/WORK/2018/February/23-02-2018-Friday/shelveeg3") as fruit:
fruit = shelve.open("D:/WORK/2018/February/23-02-2018-Friday/shelveeg3")
fruit['orange']='citrus fruit'
fruit['apple']='good for health'
fruit['lemon']='small fruit'
fruit['papaya']='good for eye'

print(fruit)
print(fruit['lemon'])

fruit['lemon']='Can Make Juice'

print(fruit)
print(fruit['lemon'])

for i in fruit:
    print(i +" - " + fruit[i])
print("="*40)

# while True:
#     var1 = input("enter any fruit key - ")
#     if var1 =='quit':
#         break
#     # print(fruit.get(var1,'entered key doent exits'))
#     if var1 in fruit:
#         print(fruit[var1])
#     else:
#         print('entered key does not exits')

#to get the shelve in sorted order
shelvesortlist = list(fruit.keys())
shelvesortlist.sort()
print(shelvesortlist)
print(fruit)
for var2 in shelvesortlist:
    print(var2+" - "+fruit[var2])
print (fruit.values())
print (fruit.items())
print (fruit.keys())
fruit.close()


#the below example is not prefect,but the thing is there is a concept of writeback and sync
#related to shelve object,which can be used to update the shelve based on memory usage
#the benefits of these will be know later i guess.


import shelve

blt = ["bread","bacon","lettuce"]
egg = ["boiled egg","Milk"]
butter = ["cheese","butter"]
pasta = ["pasta","macroni"]

with shelve.open("D:/WORK/2018/February/23-02-2018-Friday/shelveupdateeg4") as recipes:
    recipes["blt"]=blt
    recipes["egg"]=egg
    recipes["butter"]=butter
    recipes["pasta"]=pasta
    print(recipes)

    for var1 in recipes:
        print(var1,recipes[var1])

#in the eg above if we want to update the items against any key in shelve,
#if we use append method ,it wont update the shelve like check using the below code
    recipes["egg"].append("omlette")
    for var1 in recipes:
        print(var1,recipes[var1])
#we can update it correcty by changing the list itself and reassigning to the shelve
    templist = ["boiled egg","Milk","omlette"]
    recipes["egg"]=templist
    for var1 in recipes:
        print(var1,recipes[var1])

print("="*40)
with shelve.open("D:/WORK/2018/February/23-02-2018-Friday/shelveupdateeg4") as recipes:
    for var1 in recipes:
        print(var1,recipes[var1])
print('*'*40)