Python – Handling Empty Values in a Python List

listpython

Is it possible to assign a list with empty values in Python?
This is possible:

x = []

But I want to do something like:

x = [4,7,2, ,8,9,1]

with an empty value inside.
The reason is that I have a large number of lists with 7 values and sometimes one of the values are unavailable. I need to keep say 8 as x[4],9 as x[5] etc.

My thoughts:
Maybe I should just put a number like 999 inside, or a string "empty" and tell my code to ignore 999 or "empty" or whatever.

What is the best option here?

Best Answer

Use None for the "empty" value.

a = [1,2,3,4,5]
b = [11,22,None,44,55]

Related Solutions

Python List – How to Check for Empty Elements in a List

With bool(['']) you're checking if the list [''] has any contents, which it does, the contents just happen to be the empty string ''.

If you want to check whether all the elements in the list aren't 'empty' (so if the list contains the string '' it will return False) you can use the built-in function all():

all(v for v in l)

This takes every element v in list l and checks if it has a True value; if all elements do it returns True if at least one doesn't it returns False. As an example:

l = ''.split(',')

all(v for v in l)
Out[75]: False

You can substitute this with any() to perform a partial check and see if any of the items in the list l have a value of True.

A more comprehensive example* with both uses:

l = [1, 2, 3, '']

all(l)
# '' doesn't have a True value
Out[82]: False

# 1, 2, 3 have a True value
any(l)
Out[83]: True

*As @ShadowRanger pointed out in the comments, the same exact thing can be done with all(l) or any(l) since they both just accept an iterable in the end.

Best Answer

Related Solutions

Python List – How to Check for Empty Elements in a List

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