62 lines
2.0 KiB
Plaintext
62 lines
2.0 KiB
Plaintext
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This rule raises an error when the ``++dtype++`` parameter is not provided when using ``++pandas.read_csv++`` or ``++pandas.read_table++``.
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== Why is this an issue?
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The pandas library provides an easy way to load data from documents hosted locally or remotely, for example with the ``++pandas.read_csv++`` or ``++pandas.read_table++`` functions:
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[source,python]
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----
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import pandas as pd
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df = pd.read_csv("my_file.csv")
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----
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Pandas will infer the type of each columns of the CSV file and specify the datatype accordingly, making this code perfectly valid.
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However this snippet of code does not convey the proper intent of the user, and can raise questions such as:
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* What information can I access in ``++df++``?
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* What are the names of the columns available in ``++df++``?
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These questions arise as there are no descriptions of what kind of data is loaded into the data frame, making the code less understandable and harder to maintain.
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A straightforward way to fix these issues is by providing the schema of the data through the usage of the ``++dtype++`` parameter.
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== How to fix it
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To fix this issue provide the ``++dtype++`` parameter to the ``++read_csv++`` or ``++read_table++`` function.
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=== Code examples
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==== Noncompliant code example
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[source,python,diff-id=1,diff-type=noncompliant]
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----
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import pandas as pd
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def foo():
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return pd.read_csv("my_file.csv") # Noncompliant: it is unclear which type of data the data frame holds.
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----
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==== Compliant solution
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[source,python,diff-id=1,diff-type=compliant]
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----
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import pandas as pd
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def foo():
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return pd.read_csv(
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"my_file.csv",
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dtype={'name': 'str', 'age': 'int'}) # Compliant
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----
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== Resources
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=== Documentation
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* Pandas Documentation - https://pandas.pydata.org/docs/reference/api/pandas.read_csv.html#pandas-read-csv[pandas.read_csv]
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* Pandas Documentation - https://pandas.pydata.org/docs/reference/api/pandas.read_table.html#pandas-read-table[pandas.read_table]
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* Pandas Documentation - https://pandas.pydata.org/docs/user_guide/basics.html#dtypes[dtypes]
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