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csvio: Python Library for processing CSV files

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csvio is a Python library that provides a wrapper around Python’s built in csv.DictReader and csv.DictWriter, for ease of reading and writing CSV files.

Rows in a CSV are represented and processed as a list of dictionaries. Each item in this list is a dictionary that represents a row. The key, value pairs in each dictionary is a mapping between the column and its associated row value from the CSV.

Installation

pip install csvio

Documentation

Readthedocs

Reading CSVs

CSV file contents:

Supplier,Fruit,Quantity
Big Apple,Apple,1
Big Melons,Melons,2
Long Mangoes,Mango,3
Small Strawberries,Strawberry,4
>>> from csvio import CSVReader
>>> reader = CSVReader("fruit_stock.csv")
>>> reader.fieldnames
['Supplier', 'Fruit', 'Quantity']
>>> len(reader.rows)
4

>>> import json
>>> print(json.dumps(reader.rows, indent=4))
[
   {
         "Supplier": "Big Apple",
         "Fruit": "Apple",
         "Quantity": "1"
   },
   {
         "Supplier": "Big Melons",
         "Fruit": "Melons",
         "Quantity": "2"
   },
   {
         "Supplier": "Long Mangoes",
         "Fruit": "Mango",
         "Quantity": "3"
   },
   {
         "Supplier": "Small Strawberries",
         "Fruit": "Strawberry",
         "Quantity": "4"
   }
]

Writing CSVs

>>> from csvio import CSVWriter
>>> writer = CSVWriter("fruit_stock.csv", fieldnames=["Supplier", "Fruit", "Quantity"])
>>> row1 = {"Supplier": "Big Apple", "Fruit": "Apple", "Quantity": 1}
>>> writer.add_rows(row1)
>>> rows2_3_4 = [
...     {"Supplier": "Big Melons", "Fruit": "Melons", "Quantity": 2},
...     {"Supplier": "Long Mangoes", "Fruit": "Mango", "Quantity": 3},
...     {"Supplier": "Small Strawberries", "Fruit": "Strawberry", "Quantity": 4}
... ]
>>> writer.add_rows(rows2_3_4)
>>> len(writer.pending_rows)
4

>>> len(writer.rows)
0

>>> writer.flush()
>>> len(writer.pending_rows)
0

>>> len(writer.rows)
4

Once flush is called a CSV file with the name fruit_stock.csv will be written with the following contents.

Supplier,Fruit,Quantity
Big Apple,Apple,1
Big Melons,Melons,2
Long Mangoes,Mango,3
Small Strawberries,Strawberry,4

Apply processors to transform row values

Example with CSVReader

Example with CSVWriter

Create nested dictionaries with specified path

CSV Contents: fruit_stock.csv

Supplier,Fruit,Origin,Quantity
Big Apples,Apple,Spain,1
Big Melons,Melons,Italy,2
Long Mangoes,Mango,India,3
Small Strawberries,Strawberry,France,4
Short Mangoes,Mango,France,5
Sweet Strawberries,Strawberry,Spain,6
Square Apples,Apple,Italy,7
Small Melons,Melons,Italy,8
Dark Berries,Strawberry,Australia,9
Sweet Berries,Blackcurrant,Australia,10

Create dictionary with hierarchy {"Fruit": [rows]}

from csvio.csvreader import CSVReader
from json import dumps

reader = CSVReader("fruit_stock.csv")

col_order = ["Fruit"]

dict_tree= reader.rows_to_nested_dicts(col_order)

print(dumps(dict_tree, indent=4))

Output:

{
    "Apple": [
        {
            "Supplier": "Big Apples",
            "Fruit": "Apple",
            "Origin": "Spain",
            "Quantity": "1"
        },
        {
            "Supplier": "Square Apples",
            "Fruit": "Apple",
            "Origin": "Italy",
            "Quantity": "7"
        }
    ],
    "Melons": [
        {
            "Supplier": "Big Melons",
            "Fruit": "Melons",
            "Origin": "Italy",
            "Quantity": "2"
        },
        {
            "Supplier": "Small Melons",
            "Fruit": "Melons",
            "Origin": "Italy",
            "Quantity": "8"
        }
    ],
    "Mango": [
        {
            "Supplier": "Long Mangoes",
            "Fruit": "Mango",
            "Origin": "India",
            "Quantity": "3"
        },
        {
            "Supplier": "Short Mangoes",
            "Fruit": "Mango",
            "Origin": "France",
            "Quantity": "5"
        }
    ],
    "Strawberry": [
        {
            "Supplier": "Small Strawberries",
            "Fruit": "Strawberry",
            "Origin": "France",
            "Quantity": "4"
        },
        {
            "Supplier": "Sweet Strawberries",
            "Fruit": "Strawberry",
            "Origin": "Spain",
            "Quantity": "6"
        },
        {
            "Supplier": "Dark Berries",
            "Fruit": "Strawberry",
            "Origin": "Australia",
            "Quantity": "9"
        }
    ],
    "Blackcurrant": [
        {
            "Supplier": "Sweet Berries",
            "Fruit": "Blackcurrant",
            "Origin": "Australia",
            "Quantity": "10"
        }
    ]
}

Create dictionary with hierarchy {"Fruit": "Origin" : [rows]}

from csvio.csvreader import CSVReader
from json import dumps

reader = CSVReader("fruit_stock.csv")

col_order = ["Fruit", "Origin"]

dict_tree= reader.rows_to_nested_dicts(col_order)

print(dumps(dict_tree, indent=4))

Output:

{
    "Apple": {
        "Spain": [
            {
                "Supplier": "Big Apples",
                "Fruit": "Apple",
                "Origin": "Spain",
                "Quantity": "1"
            }
        ],
        "Italy": [
            {
                "Supplier": "Square Apples",
                "Fruit": "Apple",
                "Origin": "Italy",
                "Quantity": "7"
            }
        ]
    },
    "Melons": {
        "Italy": [
            {
                "Supplier": "Big Melons",
                "Fruit": "Melons",
                "Origin": "Italy",
                "Quantity": "2"
            },
            {
                "Supplier": "Small Melons",
                "Fruit": "Melons",
                "Origin": "Italy",
                "Quantity": "8"
            }
        ]
    },
    "Mango": {
        "India": [
            {
                "Supplier": "Long Mangoes",
                "Fruit": "Mango",
                "Origin": "India",
                "Quantity": "3"
            }
        ],
        "France": [
            {
                "Supplier": "Short Mangoes",
                "Fruit": "Mango",
                "Origin": "France",
                "Quantity": "5"
            }
        ]
    },
    "Strawberry": {
        "France": [
            {
                "Supplier": "Small Strawberries",
                "Fruit": "Strawberry",
                "Origin": "France",
                "Quantity": "4"
            }
        ],
        "Spain": [
            {
                "Supplier": "Sweet Strawberries",
                "Fruit": "Strawberry",
                "Origin": "Spain",
                "Quantity": "6"
            }
        ],
        "Australia": [
            {
                "Supplier": "Dark Berries",
                "Fruit": "Strawberry",
                "Origin": "Australia",
                "Quantity": "9"
            }
        ]
    },
    "Blackcurrant": {
        "Australia": [
            {
                "Supplier": "Sweet Berries",
                "Fruit": "Blackcurrant",
                "Origin": "Australia",
                "Quantity": "10"
            }
        ]
    }
}

Construct a dictionary with number of rows for each unique Origin

from csvio.csvreader import CSVReader
from json import dumps

reader = CSVReader("fruit_stock.csv")

col_order = ["Origin"]

origin_fruit_count = {}
dict_tree = reader.rows_to_nested_dicts(col_order)

for origin in dict_tree:
    origin_fruit_count.setdefault(origin, len(dict_tree[origin]))

print(dumps(origin_fruit_count, indent=4))

Output:

{
    "Spain": 2,
    "Italy": 3,
    "India": 1,
    "France": 2,
    "Australia": 2
}

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