How do i turn a list into a table in python?

There are a few useful tips to convert a Python list (or any other iterable such as a tuple) to a string for display.

First, if it is a list of strings, you may simply use join this way:

>>> mylist = ['spam', 'ham', 'eggs']
>>> print ', '.join(mylist)
spam, ham, eggs

Using the same method, you might also do this:

>>> print '\n'.join(mylist)
spam
ham
eggs

However, this simple method does not work if the list contains non-string objects, such as integers.

If you just want to obtain a comma-separated string, you may use this shortcut:

>>> list_of_ints = [80, 443, 8080, 8081]
>>> print str(list_of_ints).strip('[]')
80, 443, 8080, 8081

Or this one, if your objects contain square brackets:

>>> print str(list_of_ints)[1:-1]
80, 443, 8080, 8081

Finally, you may use map() to convert each item in the list to a string, and then join them:

>>> print ', '.join(map(str, list_of_ints))
80, 443, 8080, 8081
>>> print '\n'.join(map(str, list_of_ints))
80
443
8080
8081

In this post, you’ll learn how to transform a list into a data.table in R programming. Make sure to also visit our data.table page here, where we give an overview of the package and many related tutorials.

This tutorial consists of the following content blocks:

It’s time to dive into the examples.

Example Data & Packages

First, we need to install and load the data.table software package:

install.packages("data.table")             # Install & load data.table package
library("data.table")

Next, we construct some example data:

l_1 <- list( A = 1:5,
             B = letters[1:5],
             C = seq(0, 1, length.out = 5) )
l_1
# $A
# [1] 1 2 3 4 5
# 
# $B
# [1] "a" "b" "c" "d" "e"
# 
# $C
# [1] 0.00 0.25 0.50 0.75 1.00

Have a look at the previous RStudio console output. It shows that our example data l_1 is a list, containing three list elements, each being a vector of length five. For the creation of the list, we used seq() to create a sequence of numbers and letters[x:y] to create a sequence of letters.

Example 1: List to data.table: setDT

In Example 1, I’ll illustrate how to create a data.table from list l_1.

DT_1 <- data.table::copy(l_1)              # Replicate l_1
setDT(DT_1)                                # Transform list to data.table
DT_1

Table 1 shows the result of the previous code: a data.table. We first replicated our list l_1 and called that object DT_1 (still a list). Using setDT(), we transformed the list into a data.table. Note that the function requires that all list elements have the same length.

Example 2: List to data.table: do.call

In this example, I’ll demonstrate an alternative way of creating a data.table from a list.

DT_2 <- data.table(do.call(cbind, l_1))    # Transform list to data.table
DT_2

As shown in Table 2, the previous R programming syntax has created a data.table. As second function entry, do.call() takes a list and the first entry determines the function to be applied to the list elements. In the example, cbind() (short for column bind) sticks together the list elements of l_1 — column by column. The outer function data.table() sets the output to a data.table.

Video, Further Resources & Summary

Have a look at the following video on my YouTube channel. In the video, I demonstrate the contents of this tutorial.

The YouTube video will be added soon.

Furthermore, you might read the other articles on this website. We have released several related articles already:

• Convert Matrix to List of Column-Vectors in R
• Convert List of Vectors to Data Frame
• Convert List to Lowercase or Uppercase in R
• Convert Data Frame Columns to List Elements
• Introduction to R Programming

In summary: You have learned in this post how to create a data.frame from a list in R. Please let me know in the comments below, in case you have further questions or comments.

This page was created in collaboration with Anna-Lena Wölwer. Have a look at Anna-Lena’s author page to get further information about her academic background and the other articles she has written for Statistics Globe.

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