Get first letter of a string from column

Question

I am trying to work on the below code:

import pandas as pd

a=pd.Series([123,22,32,453,45,453,56])

b=pd.Series([234,4353,355,453,345,453,56])

df=pd.concat([a, b], axis=1)

df.columns=['First', 'Second']

I wanted to add a new column to this data frame with the first digit from values in column 'First': a) change number to string from column 'First' b) extracting the first character from newly created string c) The results from b save as new column in the data frame

I don't know how to apply this to the pandas' data frame object. I would be grateful for helping me with that.

Answer 1

Cast the dtype of the col to str, and then perform vectorized slicing calling str:

In [29]:

df['new_col'] = df['First'].astype(str).str[0]

df

Out[29]:

   First  Second new_col

0    123     234       1

1     22    4353       2

2     32     355       3

3    453     453       4

4     45     345       4

5    453     453       4

6     56      56       5

if you need to you can cast the dtype back again calling astype(int) on the column

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