CODEWITHSUNDEEP
pythonpython-3.xordereddictionary
mamat.mj
mamat.mj

Reputation: 23

How do I extract specific values from an OrderedDict?

I like to extract specific keys and store them onto a list. So far, I am able to read from MariaDB and store the rows as a dictionary (I prefer to have the output as JSON):

import pymysql
import simplejson as json
import collections
import credentials_global

conn = pymysql.connect(
    host=credentials_global.mariadb_dev_ip_address,
    user=credentials_global.mariadb_dev_username,
    password=credentials_global.mariadb_dev_password,
    port=credentials_global.mariadb_dev_port,
    database=credentials_global.mariadb_dev_db_ticketing,
)

cursor = conn.cursor()
cursor.execute("select a, b, c, d, e, f from master.orders where c = 215")
rows = cursor.fetchall()

objects_list = []
for row in rows:
    d = collections.OrderedDict()
    d["a"] = row[0]
    d["b"] = row[1]
    d["c"] = row[2]
    d["d"] = row[3]
    d["e"] = row[4]
    d["f"] = row[5]
    objects_list.append(d)

j = json.dumps(objects_list)
print(j)

This produces the output:

[
    {
        "a": 4153,
        "b": "NO_EFFECT",
        "c": "none",
        "d": "Medium",
        "e": 1,
        "f": "No Remarks",
    },
    {
        "a": 4154,
        "b": "SIGNIFICANT",
        "c": "none",
        "d": "Low",
        "e": 1,
        "f": "Test Message",
    },
]

I like to extract all occurrences of f. I have tried:

for key, value in d.items():
    print(value)

This outputs:

4153
NO_EFFECT
none
Medium
1
No Remarks

4154
SIGNIFICANT
none
Low
1
Test Message

What I prefer is to only extract f so that the output is like [No Remarks, Test Message] (I assume the sequence is maintained). Can someone please assist how I can achieve or where to look?

Thank you

Upvotes: 1

Views: 2797

Answers (3)

coldy
coldy

Reputation: 2195

Assuming the output received is over a list:
ex = [{"a": 4153, "b": "NO_EFFECT", "c": "none", "d": "Medium", "e": 1, "f": "No Remarks"}, {"a": 4154, "b": "SIGNIFICANT", "c": "none", "d": "Low", "e": 1, "f": "Test Message"}]

We can perform 2 ways, with one iterating normally not assuming over key order, another one with the order.

Normally iterating and checking (Just for explanation)

f_list = list()
for val in ex:
    for k, v in val.items():
        if k == "f":
           f_list.append(v)

print(f_list)
Output:

['No Remarks', 'Test Message']

Ordered dictionary keeps the order of keys:

f_list = list()
for val in ex:
    f_list.append(val["f"])
print(f_list)
Output:

['No Remarks', 'Test Message']

Upvotes: 0

Ron
Ron

Reputation: 119

I think the answer your looking for is

for key, value in d.items():    
    print(value[0]['f'])

first element 0 in the list, and within that list, the element f in the dictionary.

Upvotes: 0

Axeon Thra
Axeon Thra

Reputation: 364

for obj in objects_list:
    print(obj['f'])

OrderedDict keeps the order of keys (a b c ...). The order in this output comes from the order in objects_list.

To get it on an output list:

only_f_fields = [ obj['f'] for obj in objects_list ]

Upvotes: 2

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