str.ljust() not producing changes to pandas column(series) (using to sort values) - string

Question

Cabin_Fare.Cabin.head(20) (produces these results)
583 A10
208 A11
475 A14
556 A16
331 A18
284 A19
599 A20
28 A21
630 A23
867 A24
647 A26
112 A29
209 A31
185 A32
445 A34
293 A34
374 A34
806 A36
96 A5
23 A6
I assign it to x and convert the object types to string type.
x = Cabin_Fare.Cabin.astype('string')
I'm trying to push values like A5/A6 (The last two values) one space to the left, because when the column is being sorted, any values with only a len of 2 aren't being sorted properly. I'm assuming because they aren't aligned equally with those values having a len of 3.
So I tried to run this code but I'm not seeing any changes made (the A5/A6 aren't being pushed one space to the left)
for i in x[x.notnull()]:
if len(i) == 2:
i= i.ljust(3,)
Edit: I'm trying to utilize Boud's solution and I'm running into a problem because there are values/instances where only the letter (no numbers)is present.
The error shows up as:
ValueError: invalid literal for long() with base 10: ''
To circumvent this, I'm trying to add a '0' to the values where only the letter is present.
for i in x:
if len(i)==1:
i = i+'0'
However, the changes are not sticking outside of the loop, just within.

Answer 1

Your values don't have a leading space, actually. Sorting against strings will apply the alphabetical order, which is character by character. All strings start with an A, then the second character is a digit, and 5 and 6 are digits that are greater than 0, 1, 2, and 3 in your example. So the numbers are considered are numbers, but as a sequence of single digit.
If you want a sort by the numbers following A, extract the number by removing the first character, convert into int, sort that series of int, and then reindex x based on the resulting index of that proper sort:
x.reindex(x.str[1:].astype(int).sort_values().index)
Out[57]:
18 A5
19 A6
0 A10
1 A11
2 A14
3 A16
4 A18
5 A19
6 A20
7 A21
8 A23
9 A24
10 A26
11 A29
12 A31
13 A32
14 A34
15 A34
16 A34
17 A36
Name: Cabin, dtype: object