String to List Conversions in Python

Time for yet another article on data type conversions. If you haven’t done so yet, make sure to read my previous articles as well:

– String to Number Conversions

– Converting String Representations of Binary, Octal and Hexadecimal Integers

– Number to String Conversions

Today we’ll learn how to convert strings to lists.

Here’s the video version of this article:

You can enter more than one thing at a time in user input. You can enter a list:

 >>> colors = input("What are your favorite colors?")
 What are your favorite colors?
 ["green", "yellow", "blue"] 

If you echo the input, it will appear in quotes as a string.

>>> colors
'["green", "yellow", "blue"]'

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There will be no quotes if you use the print function, but still a string is returned.

>>> print(colors)
["green", "yellow", "blue"]

You can easily check what type something is by means of the type function. It turns out that colors is a string:

>>> type(colors)
<class 'str'> 

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Raw Input vs Evaluated Input

If you want a list to be returned, you can cast the input to a list by using the list function or use the eval function. The eval function is used to evaluate input. So, what we get with just input is the so-called raw input, which is a string. What we get with eval(input()) is evaluated input. There’s a difference in how these two functions work. First let’s use the list function:

>>> cities = list(input("What cities did you go to?"))
What cities did you go to?
['Rome', 'Venice', 'Florence']

Now we have a list of all the characters:

>>> cities
['[', "'", 'R', 'o', 'm', 'e', "'", ',', ' ', "'", 'V', 'e', 'n', 'i', 'c', 'e', "'", ',', ' ', "'", 'F', 'l', 'o', 'r', 'e', 'n', 'c', 'e', "'", ']']
>>> type(cities)
<class 'list'>  

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And this is what we get using the eval function:

>>> cities = eval(input("What cities did you go to?"))
What cities did you go to?
['Rome', 'Venice', 'Florence']

This is the list that we get now. This is the one we were expecting:

>>> cities
['Rome', 'Venice', 'Florence']

Now we have a list, too.

>>> type(cities)
<class 'list'> 

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