Develop Reference

Pyspark - Dynamically create schema from json files

I'm using Spark on Databricks notebooks to ingest some data from API call.
I start off by reading all the data from API response into a dataframe called df. But, I only need to few columns from API response, not all of them and also
I store the required columns and their data types in a json file
{
"structure": [
{
"column_name": "column1",
"column_type": "StringType()"
},
{
"column_name": "column2",
"column_type": "IntegerType()"
},
{
"column_name": "column3",
"column_type": "DateType()"
},
{
"column_name": "column4",
"column_type": "StringType()"
}
]
}
And then I'm building the schema using following code
with open("/dbfs/mnt/datalake/Dims/shema_json","r") as read_handle:
file_contents = json.load(read_handle)
struct_fields = []
for column in file_contents.get("structure"):
struct_fields.append(f'StructField("{column.get("column_name")}",{column.get("column_type")},True)')
new_schema = StructType(struct_fields)
Then finally, I want to create a dataframe with required columns with correct data types using this code
df_staging = spark.createDataFrame(df.rdd,schema = new_schema)
But, when I do this, I get an error message saying 'str' object has no attribute 'name'

To get a subset of columns from a dataframe you can use a simple select combined with cast:
import importlib
cols=[f"cast({c['column_name']} as {getattr(importlib.import_module('pyspark.sql.types'), c['column_type'].replace('()',''))().simpleString()})" for c in file_contents['structure']]
df.selectExpr(*cols).show()

Convert Embedded JSON Dict To Panda DataFrame Where Columns Headers Are Seperate From Values

I'm trying to create a python pandas DataFrame out of a JSON dictionary. The embedding is tripping me up.
The column headers are in a different section of the JSON file to the values.
The json looks similar to below. There is one section of column headers and multiple sections of data.
I need each column filled with the data that relates to it. So value_one in each case will fill the column under header_one and so on.
I have come close, but can't seem to get it to spit out the dataframe as described.
{
"my_data": {
"column_headers": [
"header_one",
"header_two",
"header_three"
],
"values": [
{
"data": [
"value_one",
"value_two",
"value_three"
]
},
{
"data": [
"value_one",
"value_two",
"value_three"
]
}
]
}
}

Assuming your dictionary is my_dict, try:
>>> pd.DataFrame(data=[d["data"] for d in my_dict["my_data"]["values"]],
columns=my_dict["my_data"]["column_headers"])

Using pandas.json_normalize to "unfold" a dictionary of a list of dictionaries

I am new to Python (and coding in general) so I'll do my best to explain the challenge I'm trying to work through.
I'm working with a large dataset which was exported as a CSV from a database. However, there is one column within this CSV export that contains a nested list of dictionaries (as best as I can tell). I've looked around extensively online for a solution, including on Stackoverflow, but haven't quite gotten a full solution. I think I understand conceptually what I'm trying to accomplish, but not clear as to the best method or data prepping process to use.
Here is an example of the data (pared down to just the two columns I'm interested in):
{
"app_ID": {
"0": 1abe23574,
"1": 4gbn21096
},
"locations": {
"0": "[ {"loc_id" : "abc1", "lat" : "12.3456", "long" : "101.9876"
},
{"loc_id" : "abc2", "lat" : "45.7890", "long" : "102.6543"}
]",
"1": "[ ]",
]"
}
}
Basically each app_ID can have multiple locations tied to a single ID, or it can be empty as seen above. I have attempted using some guides I found online using Panda's json_normalize() function to "unfold" or get the list of dictionaries into their own rows in a Panda dataframe.
I'd like to end up with something like this:
loc_id lat long app_ID
abc1 12.3456 101.9876 1abe23574
abc1 45.7890 102.6543 1abe23574
etc...
I am learning about how to use the different functions of json_normalize, like "record_path" and "meta", but haven't been able to get it to work yet.
I have tried loading the json file into a Jupyter Notebook using:
with open('location_json.json', 'r') as f:
data = json.loads(f.read())
df = pd.json_normalize(data, record_path = ['locations'])
but it only creates a dataframe that is 1 row and multiple columns long, where I'd like to have multiple rows generated from the inner-most dictionary that tie back to the app_ID and loc_ID fields.
Attempt at a solution:
I was able to get close to the dataframe format I wanted using:
with open('location_json.json', 'r') as f:
data = json.loads(f.read())
df = pd.json_normalize(data['locations']['0'])
but that would then require some kind of iteration through the list in order to create a dataframe, and then I'd lose the connection to the app_ID fields. (As best as I can understand how the json_normalize function works).
Am I on the right track trying to use json_normalize, or should I start over again and try a different route? Any advice or guidance would be greatly appreciated.

I can't say that suggesting you using convtools library is a good thing since you are a beginner, because this library is almost like another Python over the Python. It helps to dynamically define data conversions (generating Python code under the hood).
But anyway, here is the code if I understood the input data right:
import json
from convtools import conversion as c
data = {
"app_ID": {"0": "1abe23574", "1": "4gbn21096"},
"locations": {
"0": """[ {"loc_id" : "abc1", "lat" : "12.3456", "long" : "101.9876" },
{"loc_id" : "abc2", "lat" : "45.7890", "long" : "102.6543"} ]""",
"1": "[ ]",
},
}
# define it once and use multiple times
converter = (
c.join(
# converts "app_ID" data to iterable of dicts
(
c.item("app_ID")
.call_method("items")
.iter({"id": c.item(0), "app_id": c.item(1)})
),
# converts "locations" data to iterable of dicts,
# where each id like "0" is zipped to each location.
# the result is iterable of dicts like {"id": "0", "loc": {"loc_id": ... }}
(
c.item("locations")
.call_method("items")
.iter(
c.zip(id=c.repeat(c.item(0)), loc=c.item(1).pipe(json.loads))
)
.flatten()
),
# join on "id"
c.LEFT.item("id") == c.RIGHT.item("id"),
how="full",
)
# process results, where 0 index is LEFT item, 1 index is the RIGHT one
.iter(
{
"loc_id": c.item(1, "loc", "loc_id", default=None),
"lat": c.item(1, "loc", "lat", default=None),
"long": c.item(1, "loc", "long", default=None),
"app_id": c.item(0, "app_id"),
}
)
.as_type(list)
.gen_converter()
)
result = converter(data)
assert result == [
{'loc_id': 'abc1', 'lat': '12.3456', 'long': '101.9876', 'app_id': '1abe23574'},
{'loc_id': 'abc2', 'lat': '45.7890', 'long': '102.6543', 'app_id': '1abe23574'},
{'loc_id': None, 'lat': None, 'long': None, 'app_id': '4gbn21096'}
]

Create a data frame from a complex nested dictionary?

I have a big nested, then nested then nested json file saved as .txt format. I need to access some specific key pairs and crate a data frame or another transformed json object for further use. Here is a small sample with 2 key pairs.
[
{
"ko_id": [819752],
"concepts": [
{
"id": ["11A71731B880:http://ontology.intranet.com/Taxonomy/116#en"],
"uri": ["http://ontology.intranet.com/Taxonomy/116"],
"language": ["en"],
"prefLabel": ["Client coverage & relationship management"]
}
]
},
{
"ko_id": [819753],
"concepts": [
{
"id": ["11A71731B880:http://ontology.intranet.com/Taxonomy/116#en"],
"uri": ["http://ontology.intranet.com/Taxonomy/116"],
"language": ["en"],
"prefLabel": ["Client coverage & relationship management"]
}
]
}
]
The following code load the data as list but I need to access to the data probably as a dictionary and I need the "ko_id", "uri" and "prefLabel" from each key pair and put it to a pandas data frame or a dictionary for further analysis.
with open('sample_data.txt') as data_file:
json_sample = js.load(data_file)
The following code gives me the exact value of the first element. But donot actually know how to put it together and build the ultimate algorithm to create the dataframe.
print(sample_dict["ko_id"][0])
print(sample_dict["concepts"][0]["prefLabel"][0])
print(sample_dict["concepts"][0]["uri"][0])

for record in sample_dict:
df = pd.DataFrame(record['concepts'])
df['ko_id'] = record['ko_id']
final_df = final_df.append(df)

You can pass the data to pandas.DataFrame using a generator:
import pandas as pd
import json as js
with open('sample_data.txt') as data_file:
json_sample = js.load(data_file)
df = pd.DataFrame(data = ((key["ko_id"][0],
key["concepts"][0]["prefLabel"][0],
key["concepts"][0]["uri"][0]) for key in json_sample),
columns = ("ko_id", "prefLabel", "uri"))
Output:
>>> df
ko_id prefLabel uri
0 819752 Client coverage & relationship management http://ontology.intranet.com/Taxonomy/116
1 819753 Client coverage & relationship management http://ontology.intranet.com/Taxonomy/116

JSON to Pandas: is there a more elegant solution?

I have some JSON, returned from an API call, that looks something like this:
{
"result": {
"code": "OK",
"msg": ""
},
"report_name": "FAMOUS_DICTATORS",
"columns": [
"rank",
"name",
"deaths"
],
"data": [
{
"row": [
1,
"Mao Zedong",
63000000
]
},
{
"row": [
2,
"Jozef Stalin",
23000000
]
}
]
}
I'd like to convert the JSON into a Pandas DataFrame:
rank name deaths
1 Mao Zedong 63000000
2 Jozef Stalin 23000000
I wrote this and it works, but looks a bit ugly:
import pandas as pd
import json
columns = eval(r.content)['columns']
df = pd.DataFrame(columns = eval(r.content)['columns'])
for row in eval(r.content)['data']:
df.loc[len(df)+1] = row['row']
Is there a more elegant/Pythonic way to do this (e.g. possibly using pandas.io.json.read_json)?

The read_json function of pandas is a very tricky method to use. If you don't know with certainty the validity of your JSON object or whether its initial structure is sane enough to build a dataframe around, it's much better to stick to tried and tested methods to break your data down to something that pandas can use without issues 100%.
In your case, I suggest breaking down your data to a list of lists. Out of all that JSON, the only part you really need is in the data and column keys.
Try this:
import pandas as pd
import json
import urllib
js = json.loads(urllib.urlopen("test.json").read())
data = js["data"]
rows = [row["row"] for row in data] # Transform the 'row' keys to list of lists.
df = pd.DataFrame(rows, columns=js["columns"])
print df
This gives me the desired result:
rank name deaths
0 1 Mao Zedong 63000000
1 2 Jozef Stalin 23000000

see pandas.io.json.read_json(path_or_buf=None, orient=None, typ='frame', dtype=True, convert_axes=True, convert_dates=True, keep_default_dates=True, numpy=False, precise_float=False, date_unit=None
http://pandas.pydata.org/pandas-docs/dev/generated/pandas.io.json.read_json.html