How Can I Convert Nested Lists of Strings to Floats Using List Comprehensions in Python?

Converting Nested Lists to Floats Using List Comprehensions

When working with nested lists, it often becomes necessary to convert each element to a different data type. One common scenario is converting strings to floats. Instead of using nested loops, list comprehensions provide a concise and efficient solution.

Nested List Comprehension

To convert each element in a nested list to a float, a nested list comprehension can be used:

[[float(y) for y in x] for x in l]

This expression loops through each sublist x in the main list l and creates a new sublist containing floats converted from the strings in x. The resulting list will be of the same structure as the original list, but with floats instead of strings.

Flattened List Comprehension

If a single flattened list is desired, the loop order can be reversed:

[float(y) for x in l for y in x]

In this case, y iterates through all elements in all sublists, while x iterates through the sublists themselves. The result is a single list containing all floats derived from the nested list.

Example Usage

Consider the following nested list:

l = [['40', '20', '10', '30'], ['20', '20', '20', '20', '20', '30', '20'], ['30', '20', '30', '50', '10', '30', '20', '20', '20'], ['100', '100'], ['100', '100', '100', '100', '100'], ['100', '100', '100', '100']]

Using the nested list comprehension, the result would be:

[[40.0, 20.0, 10.0, 30.0], [20.0, 20.0, 20.0, 20.0, 20.0, 30.0, 20.0], [30.0, 20.0, 30.0, 50.0, 10.0, 30.0, 20.0, 20.0, 20.0], [100.0, 100.0], [100.0, 100.0, 100.0, 100.0, 100.0], [100.0, 100.0, 100.0, 100.0]]

Using the flattened list comprehension, the result would be:

[40.0, 20.0, 10.0, 30.0, 20.0, 20.0, 20.0, 20.0, 20.0, 30.0, 20.0, 30.0, 20.0, 30.0, 50.0, 10.0, 30.0, 20.0, 20.0, 20.0, 100.0, 100.0, 100.0, 100.0, 100.0, 100.0, 100.0, 100.0, 100.0]

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