Python：将csv文件转换为字典

Question

That's my csv file (import_inventory.csv) content:

ruby ,  rope ,  ruby  , gold coin ,  ruby  , axe

Plain text. Csv file is in the same folder as my script.

I want to open it, next add that items to my "inv" dictionary:

inv = {'rope': 1, 'torch': 6, 'gold coin': 42, 'dagger': 1}

I must use that function as default and define it (Thats my exercice):

def import_inventory(inventory, filename="import_inventory.csv"):

Next I need to print it just like that:

Inventory:
 count    item name
   ----------------
    45    gold coin
    12        arrow
     6        torch
     2       dagger
     1         rope
     1         ruby
    ----------------
  Total number of items: 67

I have function called "print_table" That is doing something like that for me. That's just for letting You know that problem for now is only with opening csv file and merging it with existing dictionary "inv"

Thanks in advance. If something is unclear, please let me know!

Answer 1

I think that should do what you want. If an item does not exist in the dictionary you have to create this item with a value of one. In all other cases you just have to add one.

   def import_inventory(inventory, filename="import_inventory.csv"):
        file = open(filename, 'r')
        data = file.readline().split(',')
        inv = inventory
        for item in data:
            item = item.strip()
            if item in inv:
                inv.update({item: inv[item]+1})
            else:
                inv.update({item: 1})
        return inv

    def print_table(inventory):
        inv = inventory
        count = 0
        print('{:>5} {:>15}'.format('count', 'item name'))
        print('---------------------')
        for item in inv:
            print('{:>5} {:>15}'.format(inv[item], item))
            count = count + inv[item]
        print('---------------------')
        print('Total number of items: ' + str(count))


    given_inventory = {'sword': 100, 'rope': 4}
    new_inventory = import_inventory(given_inventory)
    print_table(new_inventory)

Answer 2

I would design import_inventory in a more pythonic way with a context manager for interacting with plain text files and a defaultdict for counting the stock.

from collections import defaultdict
from contextlib import suppress

def import_inventory(inventory, filename):
    _inventory = defaultdict(int)
    with open(filename, encoding="UTF_8") as stream:
        for line in stream:
            for item in line.split(","):
                stock = inventory.get(item.strip(), 0)
                with suppress(KeyError):
                    del(inventory[item.strip()])
                _inventory[item.strip()] += stock + 1
    return _inventory

The interest of defaultdict is you don't have to check if your item is present or not before increasing the stock. Python defaultdict does it for you.

The function runs three steps:

1. Get the current stock for the read item. Initialize it to 0 if there isn't any stock for that item.
2. Remove the item from the current inventory in order to get the current stock only once. Monitor KeyError exception with the suppress feature.
3. Increment the new stock into _inventory (without checking if the item is already present).