How To Only Do String Manupilation On Column Of Pandas That Have 4 Digits Or Less?

I have df that looks like this: numbers 0 111 1 22222 2 3423 I want to apply a 0 to the beginning of any 4digit number, how do I do this? New df should look like t

Solution 1:

Using rjust

df=df.astype(str)
df.loc[df.numbers.str.len()==4,'numbers']=df.numbers.str.rjust(5,'0')
df
Out[370]: 
  numbers
01111222222   03423

Solution 2:

pandas.Series.str.zfill

df = df.astype(str)  # Making sure these are strings

mask = df.numbers.str.len() == 4
df.loc[mask, 'numbers'] = df.loc[mask, 'numbers'].str.zfill(5)

df

  numbers
01111222222   03423

Solution 3:

Try something like this

df['ResultingColumn'] = ['0'+str(x) for x in df['StringColumn'] if len.df['ResultingColumn'] == 4]