Dance Party2 - 7 months ago 40

Python Question

Given the following list of lists:

`a = [[2,3],[1,2,3],[1]]`

I need each list within a to have the same number of elements.

First, I need to get the longest length of any list in a.

Then, I need to ensure all lists are at least that long.

If not, I want to add a zero (0) to the end until that is true.

The desired result is:

`b = [[2,3,0],[1,2,3],[1,0,0]]`

Thanks in advance!

P.S. I also need to apply this to a Pandas Data Frame like this one:

`import pandas as pd`

b = [[2,3,0],[1,2,3],[1,0,0]]

f=pd.DataFrame({'column':b})

Answer

How about

```
pd.DataFrame(a).fillna(0)
```

to get exactly what you asked for

```
pd.Series(pd.DataFrame(a).fillna(0).astype(int).values.tolist()).to_frame('column')
```

this is also related to this question

where you can get much better performance with

```
def box(v):
lens = np.array([len(item) for item in v])
mask = lens[:,None] > np.arange(lens.max())
out = np.full(mask.shape, 0, dtype=int)
out[mask] = np.concatenate(v)
return out
pd.DataFrame(dict(columns=box(a).tolist()))
```

Source (Stackoverflow)