Pandas vs Julia - cheat sheet and comparison   

This is a Python/Pandas vs Julia cheatsheet and comparison. You can find what is the equivalent of Pandas in Julia or vice versa. You can find links to the documentation and other useful Pandas/Julia resources.

The table below show the useful links for both:

Below you can find equivalent code between Pandas and Julia. Have in mind that some examples might differ due to different indexing.

Setup

Import and package installation

import pandas as pd import numpy as np

using DataFrames using Statistics using CSV

Import libraries and modules

pip install pandas

using Pkg Pkg.add("JSON")

install package

https://pypi.org/

https://juliapackages.com/

Search Packages

Data Structures

Pandas Series vs Julia Array DataFrame comparison

s = pd.Series(['a', 'b', 'c'], index=[0 , 1, 2])

s = [1, 2, 3]

Pandas series vs Julia vector

s[0]

s[1]

Get first element of array or Series

df = pd.DataFrame( {'col_1': [11, 12, 13], 'col_2': [21, 22, 23]}, index=[0, 1, 3])

df = DataFrame(a=11:13, b=21:23)

Pandas vs Julia DataFrame

import numpy as np import pandas as pd data=np.random.randint(0,10,size=(10, 3)) df = pd.DataFrame(data, columns=list('abc'))

using Random Random.seed!(1); df = DataFrame(rand(10, 3), [:a, :b, :c])

Create random DataFrame

Read

Import Data Julia vs Pandas

df = pd.read_csv('file.csv')

df = CSV.read("file.csv", DataFrame)

Read CSV file

pd.read_json('file.json')

using JSON JSON.parsefile("file.json")

Read JSON file

pd.read_csv('https://example.com/file.csv')

A = urldownload("https://example.com/file.csv") A |> DataFrame

Read data from URL

df = pd.read_fwf('delim_file.txt')

readdlm("delim_file.txt", ' ', Int, ' ')

Read delimited file

Write

Data export - Pandas vs Julia

df.to_csv('file.csv')

CSV.write("file.csv", df)

Writes to a CSV file

df.to_json(filename)

using JSON3 JSON3.write("file.json",df1)

Writes to a file in JSON format

Inspect Data

Statistics, samples and summary of the data

df.head(6)

first(df, 6)

First n rows

df.tail(6)

last(df, 6)

Last n rows

df.describe()

describe(df)

Summary statistics

df.loc[:, :'a'].describe()

describe(df[!, [:a]])

Describe columns

df['A'].mean()

using Statistics mean(df.A)

Statistical functions

Select

Select data by index, by label, get subset

df.loc[1:3, :]

df[1:3, :]

Select first N rows - all columns

df.loc[[1, 2, 3], :]

df[[1, 2, 3], :]

Select rows by index

df.loc[:, ['a', 'b']].copy()

df[:, [:a, :b]]

Select columns by name(copy)

df.loc[:, ['a']]

df[!, [:A]]

Select columns by name(reference)

df.loc[1:3, ['b', 'a']]

df[1:3, [:b, :a]]

Subset rows and columns

df.loc[[3,1], ['b', 'a']]

df[[3, 1], [:c]]

Reverse selection

df[df['a'].isna()]

findall(ismissing, df[:, "a"])

Select NaN values

df['a'].dropna()

filter(!ismissing, df[:, "a"])

Select non NaN values

Add rows/columns

Add new columns and rows

df['new col'] = df['col'] * 100

df[!, "d"] = df[!, "a"] * 100

Add new column based on other column

df['new col'] = False

df[!, "e"] .= false

Add new column single value

df.loc[-1] = [1, 2, 3]

push!(df,[0, 0, 0])

Add new row at the end of DataFrame

df.append(df2, ignore_index = True)

append!(df,df2)

add rows from DataFrame to existing DataFrame

Drop rows/columns/nan

Drop data from DataFrame

s.drop(1)

filter!(e->e≠1,a)

(Series) Drop values from Series by index (row axis)

s.drop([1, 2])

filter!(e->e∉[1, 2],a)

(Series) Drop values from Series by index (row axis)

df.drop('b' , axis=1)

dropmissing!(df[:, ["b"]])

Drop column by name col_1 (column axis)

df.dropna()

dropmissing!(df)

Drops all rows that contain null values

df.dropna()

df[all.(!ismissing, eachrow(df)), :]

Drops all rows that contain null values

df.dropna(axis=1)

df[:, all.(!ismissing, eachcol(df))]

Drops all columns that contain null values

Sort values/index

Sorting and rank values in Pandas vs Julia

sorted([2,3,1])

sort([2,3,1])

sort array of values

sorted([2,3,1], reverse=True)

sort([2,3,1], rev=true)

sort in reverse order

df['a'].sort_values()

sort(df, [:a])

sort DataFrame by column

df.sort_values(['a', 'b'], ascending=[False, True])

sort(df, [order(:a, rev=true), :b])

sort DataFrame by multiple columns

Filter

Filter data based on multiple criteria

df.loc[:, df.isna().any()]

mapcols(x -> any(ismissing, x), df)

find columns with na

df[df['col_1'] > 100]

filter(row -> row.a > 100, df)

Values greater than X

df[(df['a']=='a')&(df['b']>=10)]

filter(row -> row.a == 'a' && row.b >= 5, df)

Filter Multiple Conditions - & - and; | - or

df[df['a'] == 'test']

df[ ( df.a .== "test" ) , :]

filter by sting value

df[(df['a'] == 'test') & (df['b'] == 'a2') ]

df[ ( df.a .== "test" ) .& ( df.b .== "a2" ), :]

combine conditions

Group by

Group by and summarize data

df.groupby('a')

groupby(df, [:a])

Group by single column

df.groupby(['a', 'b']).c.sum()

gdf = groupby(df, [:a, :b]) combine(gdf, :c => sum)

group by multiple columns and sum third

df['a'].value_counts()

combine(groupby(df, [:x1]), nrow => :count)

group by and count

Convert

Convert to date, string, numeric

df['a'].fillna(0)

replace(df.a,missing => 0)

replace NA values

df.replace('..', None)

ifelse.(df .== "..", missing, df)

convert .. to NA

df['col_1'].astype('int64')

df[!, :a] = parse.(Int64, df[!, :a])

convert string to int

pd.to_datetime(df['date'], format='%Y-%m-%d')

using Dates df.Date = Date.(df.Date, "dd-mm-yyyy")

convert string to date

Install Julia Packages

To install new packages in Julia we can also use the Julia Package manager by:

• open Linux Terminal
• start Julia - julia
• Type ] (right bracket). You don’t have to hit Return.
  • Termimal will change to (@v1.8) pkg>
• Type add <package_name> to add a package
  • you can provide the names of several packages separated by spaces.
• Control-C to exit the package manager

Example: (v1.8) pkg> add JSON StaticArrays

Differences: Julia and Pandas

Pandas and Julia are both popular tools for data analysis and manipulation. Some key differences between them:

Indexing

One big difference between Julia and Pandas is indexing:

• Julia - 1 based (can be configured)
  * What's the big deal? 0 vs 1 based indexing
  * Why does Julia adopt 1-based index?
  * Pandas - 0 based

Syntax

Personally I prefer SQL syntax over both Julia and Pandas. I can work fine with both of them. As I have more experience with Python I would go with Pandas. Some people consider Julia to have better syntax since it was designed for data science. Example of syntax difference between Julia and Pandas:

# pandas
import pandas as pd
df = pd.read_csv('sales_data.csv')
totals = df.groupby('product')['sales'].sum()

# julia
using DataFrames
using CSV
df = DataFrame(CSV.read("sales_data.csv"))
totals = combine(groupby(df, :product), :sales => sum)

Performance

In general Julia is faster for most operations and bigger datasets. For smaller datasets Pandas might be close or even better than Julia. The reason is for compilation time for Julia.

To test performance we can use dataset with 10M rows - Game Recommendations on Steam:

# pandas
%%time
import pandas as pd
df = pd.read_csv('recommendations.csv')
df['hours'].mean()

# julia
@time begin
using CSV, DataFrames
df = CSV.File("recommendations.csv") |> DataFrame
result = mean(df[:, "hours"])
end

The results are:

• Pandas
  • CPU times: user 5.67 s, sys: 1.85 s, total: 7.52 s
  • Wall time: 7.71 s
• Julia
  • 7.257497 seconds (1.13 k allocations: 1.349 GiB, 2.63% gc time)

While for dataset - 12M rows we get:

• Pandas
  • CPU times: user 34.8 s, sys: 3.74 s, total: 38.5 s
  • Wall time: 42.4 s
• Julia
  • 29.964544 seconds (162.12 M allocations: 9.878 GiB, 15.79% gc time)

First julia execution is slower so we take the second one.

Libraries and Ecosystem

Pandas has a bigger community and ecosystem. The Python libraries offers greater variety of Packages in many areas:

• web scraping
• data science
• science
• etc

Language Features

I prefer Julia for distributed computing and parallel computing. Pandas seems for me much better for visualization and EDA.

Learning Curve

Again it depends on personal choice. Python is considered as one of the best programming languages for beginners. Julia surpassed Python in recent surveys for loved language:

stackoverflow survey - Most loved, dreaded, and wanted

Note: I need to add that I'm still learning and discovering Julia - so so statements above might change in future :)

Pandas vs Julia docs

Summary

In summary, Pandas and Julia are both powerful tools for data analysis, but they have different strengths and weaknesses.

Pandas has a larger ecosystem of tools and is generally easier to learn. Julia is faster and has some unique language features that can make it more powerful for certain types of data analysis tasks.

Ultimately, the choice between Pandas and Julia depends on your specific requirements and preferences.

Resources

• Julia Comparison with the Python package Pandas
• Pandas Cheat Sheet for Data Science
• Pandas vs SQL Cheat Sheet
• julia notebook
• pandas notebook

Cheatsheet Image