pandas on Snowflake¶

Benefits of using pandas on Snowflake¶

• Meeting Python developers where they are – pandas on Snowflake offers a familiar interface to Python developers by providing a pandas-compatible layer that can run natively in Snowflake.

• Scalable distributed pandas – pandas on Snowflake bridges the convenience of pandas with the scalability of Snowflake by leveraging existing query optimization techniques in Snowflake. Minimal code rewrites are required, simplifying the migration journey, so you can seamlessly move from prototype to production.

• Security and governance – Data does not leave Snowflake’s secure platform. pandas on Snowflake allows uniformity within data organizations on how data is accessed, and allows for easier auditing and governance.

• No additional compute infrastructure to manage and tune – pandas on Snowflake leverages the Snowflake’s powerful compute engine, so you do not need to set up or manage any additional compute infrastructure.

When should I use pandas on Snowflake¶

You should use pandas on Snowflake if any of the following is true:

• You are familiar with the pandas API and the broader PyData ecosystem

• You work in a team with others who are familiar with pandas and want to collaborate on the same codebase

• You have existing code written in pandas

• Your workflow has order-related needs, as supported by pandas DataFrames. For example, you need the dataset to be in the same order for the entire workflow

• You prefer more accurate code completion from AI-based copilot tools

Getting started with pandas on Snowflake¶

To install pandas on Snowflake, you can use conda or pip to install the package. For detailed instructions, see Installation.

pip install "snowflake-snowpark-python[modin]"

Once pandas on Snowflake is installed, instead of importing pandas as import pandas as pd, use the following two lines:

import modin.pandas as pd
import snowflake.snowpark.modin.plugin

Here is an example of how you can start using pandas on Snowflake through the pandas on Snowpark Python library with Modin.

import modin.pandas as pd

# Import the Snowpark plugin for modin.
import snowflake.snowpark.modin.plugin

# Create a Snowpark session with a default connection.
from snowflake.snowpark.session import Session
session = Session.builder.create()

# Create a Snowpark pandas DataFrame from existing Snowflake table
df = pd.read_snowflake('SNOWFALL')

# Alternatively, create a Snowpark pandas DataFrame with sample data.
df = pd.DataFrame([[1, 'Big Bear', 8],[2, 'Big Bear', 10],[3, 'Big Bear', None],
                    [1, 'Tahoe', 3],[2, 'Tahoe', None],[3, 'Tahoe', 13],
                    [1, 'Whistler', None],['Friday', 'Whistler', 40],[3, 'Whistler', 25]],
                    columns=["DAY", "LOCATION", "SNOWFALL"])

# Inspect the DataFrame
df

      DAY  LOCATION  SNOWFALL
0       1  Big Bear       8.0
1       2  Big Bear      10.0
2       3  Big Bear       NaN
3       1     Tahoe       3.0
4       2     Tahoe       NaN
5       3     Tahoe      13.0
6       1  Whistler       NaN
7  Friday  Whistler      40.0
8       3  Whistler      25.0

# In-place point update to fix data error.
df.loc[df["DAY"]=="Friday","DAY"]=2

# Inspect the columns after update.
# Note how the data type is updated automatically after transformation.
df["DAY"]

0    1
1    2
2    3
3    1
4    2
5    3
6    1
7    2
8    3
Name: DAY, dtype: int64

# Drop rows with null values.
df.dropna()

  DAY  LOCATION  SNOWFALL
0   1  Big Bear       8.0
1   2  Big Bear      10.0
3   1     Tahoe       3.0
5   3     Tahoe      13.0
7   2  Whistler      40.0
8   3  Whistler      25.0

# Compute the average daily snowfall across locations.
df.groupby("LOCATION").mean()["SNOWFALL"]

LOCATION
Big Bear     9.0
Tahoe        8.0
Whistler    32.5
Name: SNOWFALL, dtype: float64

Using pandas on Snowflake with Snowpark DataFrames¶

The pandas on Snowflake and DataFrame API is highly interoperable, so you can build a pipeline that leverages both APIs.

You can use the following operations to do conversions between Snowpark DataFrames and Snowpark pandas DataFrames:

Whenever possible, we advise using read_snowflake to read the table from Snowflake directly instead of converting it to and from a Snowpark DataFrame to avoid unnecessary conversion costs.

For more information, see Snowpark DataFrames vs Snowpark pandas DataFrame: Which should I choose?.

How pandas on Snowflake compares to native pandas¶

pandas on Snowflake and native pandas have similar DataFrame APIs with matching signatures and similar semantics. pandas on Snowflake provides the same API signature as native pandas (pandas 2.2.1) and provides scalable computation with Snowflake. pandas on Snowflake respects the semantics described in the native pandas documentation as much as possible, but it uses the Snowflake computation and type system. However, when native pandas executes on a client machine, it uses the Python computation and type system. For information about the type mapping between pandas on Snowflake and Snowflake, see Data types.

Like native pandas, pandas on Snowflake also has the notion of an index and maintains row ordering. However, their distinct execution environments cause certain nuanced differences in their behavior. This section calls out the key differences to be aware of.

pandas on Snowflake is best used with data which is already in Snowflake, but you can use the following operations to convert between native pandas and pandas on Snowflake:

Installation¶

Prerequisites: Python 3.9, 3.10 or 3.11, modin version 0.28.1, and pandas version 2.2.1 are required.

To install pandas on Snowflake in your development environment, follow these steps:

1. Change to your project directory and activate your Python virtual environment.

   Note

   The API is under active development, so we recommend installing it in a Python virtual environment rather than system-wide. This practice allows each project you create to use a specific version, insulating you from changes in future versions.

   You can create a Python virtual environment for a particular Python version using tools like Anaconda, Miniconda, or virtualenv.

   For example, to use conda to create a Python 3.9 virtual environment, type:

   conda create --name snowpark_pandas python=3.9
   conda activate snowpark_pandas
   

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   Note

   If you previously installed an older version of pandas on Snowflake using Python 3.8 and pandas 1.5.3, you will need to upgrade your Python and pandas versions as described above. Follow the steps to create a new environment with Python 3.9, 3.10, or 3.11.

2. Install the Snowpark Python library with Modin.

   pip install "snowflake-snowpark-python[modin]"
   

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   or

   conda install snowflake-snowpark-python modin==0.28.1
   

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Note

Make sure snowflake-snowpark-python version 1.17.0 or later is installed.

Authenticating to Snowflake¶

Before using pandas on Snowflake , you must establish a session with the Snowflake database. You can use a config file to choose the connection parameters for your session or you can enumerate them in your code. For more information, see Creating a Session for Snowpark Python. If a unique active Snowpark Python session exists, pandas on Snowflake will automatically use it. For example:

import modin.pandas as pd
import snowflake.snowpark.modin.plugin
from snowflake.snowpark import Session

CONNECTION_PARAMETERS = {
    'account': '<myaccount>',
    'user': '<myuser>',
    'password': '<mypassword>',
    'role': '<myrole>',
    'database': '<mydatabase>',
    'schema': '<myschema>',
    'warehouse': '<mywarehouse>',
}
session = Session.builder.configs(CONNECTION_PARAMETERS).create()

# pandas on Snowflake will automatically pick up the Snowpark session created above.
# It will use that session to create new DataFrames.
df = pd.DataFrame([1, 2])
df2 = pd.read_snowflake('CUSTOMER')

The pd.session is a Snowpark session, so you can do anything with it that you can do with any other Snowpark session. For example, you can use it to execute an arbitrary SQL query, which results in a Snowpark DataFrame as per the Session API, but take note that the results of this will be a Snowpark DataFrame, not a Snowpark pandas DataFrame.

# pd.session is the session that pandas on Snowflake is using for new DataFrames.
# In this case it is the same as the Snowpark session that we've created.
assert pd.session is session

# Run SQL query with returned result as Snowpark DataFrame
snowpark_df = pd.session.sql('select * from customer')
snowpark_df.show()

Alternatively, you can configure your Snowpark connection parameters in a configuration file. This eliminates the need to enumerate connection parameters in your code, allowing you to write your pandas on Snowflake code almost as you would normally write pandas code. To achieve this, create a configuration file located at ~/.snowflake/connections.toml that looks something like this:

default_connection_name = "default"

[default]
account = "<myaccount>"
user = "<myuser>"
password = "<mypassword>"
role="<myrole>"
database = "<mydatabase>"
schema = "<myschema>"
warehouse = "<mywarehouse>"

Then in the code, you only need to use snowflake.snowpark.Session.builder.create() to create a session using these credentials.

import modin.pandas as pd
import snowflake.snowpark.modin.plugin
from snowflake.snowpark import Session

# Session.builder.create() will create a default Snowflake connection.
Session.builder.create()
# create a DataFrame.
df = pd.DataFrame([[1, 2], [3, 4]])

You can also create multiple Snowpark sessions, then assign one of them to pandas on Snowflake. pandas on Snowflake only uses one session, so you have to explicitly assign one of the sessions to pandas on Snowflake with pd.session = pandas_session.

import modin.pandas as pd
import snowflake.snowpark.modin.plugin
from snowflake.snowpark import Session

pandas_session = Session.builder.configs({"user": "<user>", "password": "<password>", "account": "<account1>").create()
other_session = Session.builder.configs({"user": "<user>", "password": "<password>", "account": "<account2>").create()
pd.session = pandas_session
df = pd.DataFrame([1, 2, 3])

The following example shows that trying to use pandas on Snowflake when there is no active Snowpark session will raise a SnowparkSessionException with an error like “pandas on Snowflake requires an active snowpark session, but there is none.” Once you create a session, you can use pandas on Snowflake. For example:

import modin.pandas as pd
import snowflake.snowpark.modin.plugin

df = pd.DataFrame([1, 2, 3])

The following example shows that trying to use pandas on Snowflake when there are multiple active Snowpark sessions will cause a SnowparkSessionException with a message like, “There are multiple active snowpark sessions, but you need to choose one for pandas on Snowflake.”

import modin.pandas as pd
import snowflake.snowpark.modin.plugin
from snowflake.snowpark import Session

pandas_session = Session.builder.configs({"user": "<user>", "password": "<password>", "account": "<account1>"}).create()
other_session = Session.builder.configs({"user": "<user>", "password": "<password>", "account": "<account2>"}).create()
df = pd.DataFrame([1, 2, 3])

API Reference¶

See the pandas on Snowflake API reference for the full list of currently implemented APIs and methods available.

For a full list of supported operations, see the following tables in pandas on Snowflake reference:

• pandas general utilities supported APIs

• Series supported APIs

• DataFrame supported APIs

• Index supported APIs

• Windows supported APIs

• GroupBy supported APIs

• Resampler supported APIs

• DatetimeProperties supported APIs

• StringMethods supported APIs

Using pandas on Snowflake with Snowflake notebooks¶

To use pandas on Snowflake in Snowflake notebooks, see pandas on Snowflake in notebooks.

Using pandas on Snowflake in stored procedures¶

You can use pandas on Snowflake in a stored procedure to build a data pipeline and schedule the execution of the stored procedure with tasks.

from snowflake.snowpark.context import get_active_session
session = get_active_session()

from snowflake.snowpark import Session

def data_transformation_pipeline(session: Session) -> str:
  import modin.pandas as pd
  import snowflake.snowpark.modin.plugin
  from datetime import datetime
  # Create a Snowpark pandas DataFrame with sample data.
  df = pd.DataFrame([[1, 'Big Bear', 8],[2, 'Big Bear', 10],[3, 'Big Bear', None],
                     [1, 'Tahoe', 3],[2, 'Tahoe', None],[3, 'Tahoe', 13],
                     [1, 'Whistler', None],['Friday', 'Whistler', 40],[3, 'Whistler', 25]],
                      columns=["DAY", "LOCATION", "SNOWFALL"])
  # Drop rows with null values.
  df = df.dropna()
  # In-place point update to fix data error.
  df.loc[df["DAY"]=="Friday","DAY"]=2
  # Save Results as a Snowflake Table
  timestamp = datetime.now().strftime("%Y_%m_%d_%H_%M")
  save_path = f"OUTPUT_{timestamp}"
  df.to_snowflake(name=save_path, if_exists="replace", index=False)
  return f'Transformed DataFrame saved to {save_path}.'


  dt_pipeline_sproc = session.sproc.register(name="run_data_transformation_pipeline_sp",
                             func=data_transformation_pipeline,
                             replace=True,
                             packages=['modin', 'snowflake-snowpark-python'])

To call the stored procedure, you can run dt_pipeline_sproc() in Python or CALL run_data_transformation_pipeline_sp() in SQL.

To schedule the stored procedure as a task, you can use the Snowflake Python API to create a task.

Using pandas on Snowflake with third-party libraries¶

When calling third-party library APIs with a Snowpark pandas DataFrame, we recommend converting the Snowpark pandas DataFrame to a pandas DataFrame by calling to_pandas() before passing the DataFrame to the third-party library call.

pandas on Snowflake currently has limited compatibility for certain NumPy and Matplotlib APIs, such as distributed implementation for np.where and interoperability with df.plot. Converting Snowpark pandas DataFrames via to_pandas() when working with these third-party libraries will avoid multiple I/O calls.

Here is an example with Altair for visualization and scikit-learn for machine learning.

# Create a Snowpark session with a default connection.
session = Session.builder.create()

train = pd.read_snowflake('TITANIC')

train[['Pclass', 'Parch', 'Sex', 'Survived']].head()

    Pclass  Parch     Sex       Survived
0       3      0     male               0
1       1      0   female               1
2       3      0   female               1
3       1      0   female               1
4       3      0     male               0

import altair as alt
# Convert to pandas DataFrame
train_df_pandas = train.to_pandas()
survived_per_age_plot = alt.Chart(train_df_pandas).mark_bar(
).encode(
    x=alt.X('Age', bin=alt.Bin(maxbins=25)),
    y='count()',
    column='Survived:N',
    color='Survived:N',
).properties(
    width=300,
    height=300
).configure_axis(
    grid=False
)
survived_per_age_plot

We can now use scikit-learn to train a simple model after converting to pandas.

feature_cols = ['Pclass', 'Parch']
# Convert features DataFrame to pandas DataFrames
X_pandas = train_snowpark_pandas.loc[:, feature_cols].to_pandas()
# Convert labels Series to pandas Series
y_pandas = train_snowpark_pandas["Survived"].to_pandas()

from sklearn.linear_model import LogisticRegression

logreg = LogisticRegression()

logreg.fit(X_pandas, y_pandas)

y_pred_pandas = logreg.predict(X_pandas)

acc_eval = accuracy_score(y_pandas, y_pred_pandas)

Limitations¶

pandas on Snowflake has the following limitations:

• pandas on Snowflake provides no guarantee of compatibility with OSS third-party libraries. Starting with version 1.14.0a1, however, Snowpark pandas introduces limited compatibility for NumPy, specifically for np.where usage. For more information, see NumPy Interoperability.

  When calling third-party library APIs with a Snowpark pandas DataFrame, Snowflake recommends that you convert the Snowpark pandas DataFrame to a pandas DataFrame by calling to_pandas() before passing the DataFrame to the third-party library call. For more information, see Using pandas on Snowflake with third-party libraries.

• pandas on Snowflake is not integrated with Snowpark ML. When using Snowpark ML, we recommend that you convert the Snowpark pandas DataFrame to a Snowpark DataFrame using to_snowpark() before calling Snowpark ML.

• Lazy MultiIndex objects are not supported. When MultiIndex is used, it returns a native pandas MultiIndex object, which requires pulling all data to the client side.

• Not all pandas APIs have a distributed implementation yet in pandas on Snowflake. For unsupported APIs, NotImplementedError is thrown. Operations that have no distributed implementation fall back to a stored procedure. For information about supported APIs, refer to the API reference documentation.

• pandas on Snowflake requires a specific pandas version. pandas on Snowflake requires pandas 2.2.1, and only provides compatibility with pandas 2.2.1.

• pandas on Snowflake cannot be referenced within the pandas on Snowflake apply() function. You can only use native pandas inside apply().

Troubleshooting¶

This section describes troubleshooting tips when using pandas on Snowflake.

• When troubleshooting, try running the same operation on a native pandas DataFrame (or a sample) to see if the same error persists. This approach might provide hints on how to fix your query. For example:

  df = pd.DataFrame({"a": [1,2,3], "b": ["x", "y", "z"]})
  # Running this in Snowpark pandas throws an error
  df["A"].sum()
  # Convert a small sample of 10 rows to pandas DataFrame for testing
  pandas_df = df.head(10).to_pandas()
  # Run the same operation. KeyError indicates that the column reference is incorrect
  pandas_df["A"].sum()
  # Fix the column reference to get the Snowpark pandas query working
  df["a"].sum()
  

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• If you have a long-running notebook opened, note that by default Snowflake sessions timeout after the session is idle for 240 minutes (4 hours). When the session expires, you will get the following error if you run additional pandas on Snowflake queries: “Authentication token has expired. The user must authenticate again.” At this point, you must re-establish the connection to Snowflake again. This may result in loss of any unpersisted session variables. For more information about how to configure the session idle timeout parameter, see Session Policies.

Best practices¶

This section describes best practices to follow when using pandas on Snowflake.

• Avoid using iterative code patterns, such as for loops, iterrows, and iteritems. Iterative code patterns quickly increase the generated query complexity. Let pandas on Snowflake perform the data distribution and computation parallelization rather than the client code. When it comes to iterative code patterns, try to look for operations that can be performed on the whole DataFrame and use the corresponding operations instead.

for i in np.arange(0, 50):
  if i % 2 == 0:
    data = pd.concat([data, pd.DataFrame({'A': i, 'B': i + 1}, index=[0])], ignore_index=True)
  else:
    data = pd.concat([data, pd.DataFrame({'A': i}, index=[0])], ignore_index=True)

# Instead of creating one DataFrame per row and concatenating them,
# try to directly create the DataFrame out of the data, like this:

data = pd.DataFrame(
      {
          "A": range(0, 50),
          "B": [i + 1 if i % 2 == 0 else None for i in range(50)],
      },
)

• Avoid calling apply, applymap and transform, which are eventually implemented with UDFs or UDTFs, which might not be as performant as regular SQL queries. If the function applied has an equivalent DataFrame or series operation, use that operation instead. For example, instead of df.groupby('col1').apply('sum'), directly call df.groupby('col1').sum().

• Call to_pandas() before passing the DataFrame or series to a third-party library call. pandas on Snowflake does not provide a compatibility guarantee with third-party libraries.

• Use a materialized regular Snowflake table to avoid extra I/O overhead. pandas on Snowflake works on top of a data snapshot that only works for regular tables. For other types, including external tables, views, and Apache Iceberg™ tables, a temporary table is created before taking the snapshot, which introduces extra materialization overhead.

• pandas on Snowflake provides fast and zero copy clone capability while creating DataFrames from Snowflake tables using read_snowflake. However, the snapshot capability is only provided for regular Snowflake tables under normal databases. Extra materialization to regular Snowflake tables will be introduced when loading tables with types like hybrid, iceberg etc., or tables under shared databases. The snapshot is required to provide data consistency and ordering guarantee, and there is currently no other way to work around the extra materialization, please try to use normal Snowflake tables as much as possible when using pandas on Snowflake.

• Double check the result type before proceeding to other operations, and do explicit type casting with astype if needed.

  Due to limited type inference capability, if no type hint is given, df.apply will return results of object (variant) type even if the result contains all integer values. If other operations require the dtype to be int, you can do an explicit type casting by calling the astype method to correct the column type before you continue.

• Avoid calling APIs that require evaluation and materialization if not necessary.

  APIs that don’t return Series or Dataframe require eager evaluation and materialization to produce the result in the correct type. Same for plotting methods. Reduce calls to those APIs to minimize unnecessary evaluations and materialization.

• Avoid calling np.where(<cond>, <scalar>, n) on large datasets. The <scalar> will be broadcast to a DataFrame the size of <cond>, which may be slow.

• When working with iteratively built queries, df.cache_result can be used to materialize intermediate results to reduce the repeated evaluation and improve the latency and reduce complexity of the overall query. For example:

  df = pd.read_snowflake('pandas_test')
  df2 = pd.pivot_table(df, index='index_col', columns='pivot_col') # expensive operation
  df3 = df.merge(df2)
  df4 = df3.where(df2 == True)
  

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  In the example above, the query to produce df2 is expensive to compute, and is reused in the creation of both df3 and df4. Materializing df2 into a temporary table (making subsequent operations involving df2 a table scan instead of a pivot) can reduce the overall latency of the code block:

  df = pd.read_snowflake('pandas_test')
  df2 = pd.pivot_table(df, index='index_col', columns='pivot_col') # expensive operation
  df2.cache_result(inplace=True)
  df3 = df.merge(df2)
  df4 = df3.where(df2 == True)
  

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Examples¶

Here is a code example with pandas operations. We start with a Snowpark pandas DataFrame named pandas_test, which contains three columns: COL_STR, COL_FLOAT, and COL_INT. To view the notebook associated with these examples, see the pandas on Snowflake examples in the Snowflake-Labs repository.

import modin.pandas as pd
import snowflake.snowpark.modin.plugin

from snowflake.snowpark import Session

CONNECTION_PARAMETERS = {
    'account': '<myaccount>',
    'user': '<myuser>',
    'password': '<mypassword>',
    'role': '<myrole>',
    'database': '<mydatabase>',
    'schema': '<myschema>',
    'warehouse': '<mywarehouse>',
}
session = Session.builder.configs(CONNECTION_PARAMETERS).create()

df = pd.DataFrame([['a', 2.1, 1],['b', 4.2, 2],['c', 6.3, None]], columns=["COL_STR", "COL_FLOAT", "COL_INT"])

df

  COL_STR    COL_FLOAT    COL_INT
0       a          2.1        1.0
1       b          4.2        2.0
2       c          6.3        NaN

We save the DataFrame as a Snowflake table named pandas_test which we will use throughout our examples.

df.to_snowflake("pandas_test", if_exists='replace',index=False)

Next, we create a DataFrame from the Snowflake table. We drop the column COL_INT and then save the result back to Snowflake with a column named row_position.

# Create a DataFrame out of a Snowflake table.
df = pd.read_snowflake('pandas_test')

df.shape

(3, 3)

df.head(2)

    COL_STR  COL_FLOAT  COL_INT
0         a        2.1        1
1         b        4.2        2

df.dropna(subset=["COL_FLOAT"], inplace=True)

df

    COL_STR  COL_FLOAT  COL_INT
0         a        2.1        1
1         c        6.3        2

df.shape

(2, 3)

df.dtypes

COL_STR       object
COL_FLOAT    float64
COL_INT        int64
dtype: object

# Save the result back to Snowflake with a row_pos column.
df.reset_index(drop=True).to_snowflake('pandas_test2', if_exists='replace', index=True, index_label=['row_pos'])

You end up with a new table, pandas_test2, which looks like this:

     row_pos  COL_STR  COL_FLOAT  COL_INT
0          1         a       2.0        1
1          2         b       4.0        2

# Reading and writing to Snowflake
df = pd.DataFrame({"fruit": ["apple", "orange"], "size": [3.4, 5.4], "weight": [1.4, 3.2]})
df.to_snowflake("test_table", if_exists="replace", index=False )

df_table = pd.read_snowflake("test_table")


# Generate sample CSV file
with open("data.csv", "w") as f:
    f.write('fruit,size,weight\napple,3.4,1.4\norange,5.4,3.2')
# Read from local CSV file
df_csv = pd.read_csv("data.csv")

# Generate sample JSON file
with open("data.json", "w") as f:
    f.write('{"fruit":"apple", "size":3.4, "weight":1.4},{"fruit":"orange", "size":5.4, "weight":3.2}')
# Read from local JSON file
df_json = pd.read_json('data.json')

# Upload data.json and data.csv to Snowflake stage named @TEST_STAGE
# Read CSV and JSON file from stage
df_csv = pd.read_csv('@TEST_STAGE/data.csv')
df_json = pd.read_json('@TEST_STAGE/data.json')

df = pd.DataFrame({"a": [1,2,3], "b": ["x", "y", "z"]})
df.columns

Index(['a', 'b'], dtype='object')

df.index

Index([0, 1, 2], dtype='int8')

df["a"]

0    1
1    2
2    3
Name: a, dtype: int8

df["b"]

0    x
1    y
2    z
Name: b, dtype: object

df.iloc[0,1]

'x'

df.loc[df["a"] > 2]

a  b
2  3  z

df.columns = ["c", "d"]
df

     c  d
0    1  x
1    2  y
2    3  z

df = df.set_index("c")
df

   d
c
1  x
2  y
3  z

df.rename(columns={"d": "renamed"})

    renamed
c
1       x
2       y
3       z

import numpy as np
df = pd.DataFrame([[np.nan, 2, np.nan, 0],
                [3, 4, np.nan, 1],
                [np.nan, np.nan, np.nan, np.nan],
                [np.nan, 3, np.nan, 4]],
                columns=list("ABCD"))
df

     A    B   C    D
0  NaN  2.0 NaN  0.0
1  3.0  4.0 NaN  1.0
2  NaN  NaN NaN  NaN
3  NaN  3.0 NaN  4.0

df.isna()

       A      B     C      D
0   True  False  True  False
1  False  False  True  False
2   True   True  True   True
3   True  False  True  False

df.fillna(0)

     A    B    C    D
0   0.0  2.0  0.0  0.0
1   3.0  4.0  0.0  1.0
2   0.0  0.0  0.0  0.0
3   0.0  3.0  0.0  4.0

df.dropna(how="all")

     A    B   C    D
0   NaN  2.0 NaN  0.0
1   3.0  4.0 NaN  1.0
3   NaN  3.0 NaN  4.0

df = pd.DataFrame({"int": [1,2,3], "str": ["4", "5", "6"]})
df

   int str
0    1   4
1    2   5
2    3   6

df_float = df.astype(float)
df_float

   int  str
0  1.0  4.0
1  2.0  5.0
2  3.0  6.0

df_float.dtypes

int    float64
str    float64
dtype: object

pd.to_numeric(df.str)

0    4.0
1    5.0
2    6.0
Name: str, dtype: float64

df = pd.DataFrame({'year': [2015, 2016],
                'month': [2, 3],
                'day': [4, 5]})
pd.to_datetime(df)

0   2015-02-04
1   2016-03-05
dtype: datetime64[ns]

df_1 = pd.DataFrame([[1,2,3],[4,5,6]])
df_2 = pd.DataFrame([[6,7,8]])
df_1.add(df_2)

    0    1     2
0  7.0  9.0  11.0
1  NaN  NaN   NaN

s1 = pd.Series([1, 2, 3])
s2 = pd.Series([2, 2, 2])
s1 + s2

0    3
1    4
2    5
dtype: int64

df = pd.DataFrame({"A": [1,2,3], "B": [4,5,6]})
df["A+B"] = df["A"] + df["B"]
df

   A  B  A+B
0  1  4    5
1  2  5    7
2  3  6    9

df = pd.DataFrame([[1, 2, 3],
                [4, 5, 6],
                [7, 8, 9],
                [np.nan, np.nan, np.nan]],
                columns=['A', 'B', 'C'])
df.agg(['sum', 'min'])

        A     B     C
sum  12.0  15.0  18.0
min   1.0   2.0   3.0

df.median()

A    4.0
B    5.0
C    6.0
dtype: float64

df1 = pd.DataFrame({'lkey': ['foo', 'bar', 'baz', 'foo'],
                    'value': [1, 2, 3, 5]})
df1

  lkey  value
0  foo      1
1  bar      2
2  baz      3
3  foo      5

df2 = pd.DataFrame({'rkey': ['foo', 'bar', 'baz', 'foo'],
                    'value': [5, 6, 7, 8]})
df2

  rkey  value
0  foo      5
1  bar      6
2  baz      7
3  foo      8

df1.merge(df2, left_on='lkey', right_on='rkey')

  lkey  value_x rkey  value_y
0  foo        1  foo        5
1  foo        1  foo        8
2  bar        2  bar        6
3  baz        3  baz        7
4  foo        5  foo        5
5  foo        5  foo        8

df = pd.DataFrame({'key': ['K0', 'K1', 'K2', 'K3', 'K4', 'K5'],
                'A': ['A0', 'A1', 'A2', 'A3', 'A4', 'A5']})
df

  key   A
0  K0  A0
1  K1  A1
2  K2  A2
3  K3  A3
4  K4  A4
5  K5  A5

other = pd.DataFrame({'key': ['K0', 'K1', 'K2'],
                    'B': ['B0', 'B1', 'B2']})
df.join(other, lsuffix='_caller', rsuffix='_other')

  key_caller   A key_other     B
0         K0  A0        K0    B0
1         K1  A1        K1    B1
2         K2  A2        K2    B2
3         K3  A3      None  None
4         K4  A4      None  None
5         K5  A5      None  None

df = pd.DataFrame({'Animal': ['Falcon', 'Falcon','Parrot', 'Parrot'],
               'Max Speed': [380., 370., 24., 26.]})

df

   Animal  Max Speed
0  Falcon      380.0
1  Falcon      370.0
2  Parrot       24.0
3  Parrot       26.0

df.groupby(['Animal']).mean()

        Max Speed
Animal
Falcon      375.0
Parrot       25.0

df = pd.DataFrame({"A": ["foo", "foo", "foo", "foo", "foo",
                        "bar", "bar", "bar", "bar"],
                "B": ["one", "one", "one", "two", "two",
                        "one", "one", "two", "two"],
                "C": ["small", "large", "large", "small",
                        "small", "large", "small", "small",
                        "large"],
                "D": [1, 2, 2, 3, 3, 4, 5, 6, 7],
                "E": [2, 4, 5, 5, 6, 6, 8, 9, 9]})
df

     A    B      C  D  E
0  foo  one  small  1  2
1  foo  one  large  2  4
2  foo  one  large  2  5
3  foo  two  small  3  5
4  foo  two  small  3  6
5  bar  one  large  4  6
6  bar  one  small  5  8
7  bar  two  small  6  9
8  bar  two  large  7  9

pd.pivot_table(df, values='D', index=['A', 'B'],
                   columns=['C'], aggfunc="sum")

    C    large  small
A   B
bar one    4.0      5
    two    7.0      6
foo one    4.0      1
    two    NaN      6

df = pd.DataFrame({'foo': ['one', 'one', 'one', 'two', 'two', 'two'],
                'bar': ['A', 'B', 'C', 'A', 'B', 'C'],
                'baz': [1, 2, 3, 4, 5, 6],
                'zoo': ['x', 'y', 'z', 'q', 'w', 't']})
df

   foo bar  baz zoo
0  one   A    1   x
1  one   B    2   y
2  one   C    3   z
3  two   A    4   q
4  two   B    5   w
5  two   C    6   t

Resources¶

• Quickstart: Getting Started with pandas on Snowflake

• Quickstart: Data Engineering Pipelines with Snowpark Python