Adding a DataFrame column with len() of another column's values

Question

I\'m having a problem trying to get a character count column of the string values in another column, and haven\'t figured out how to do it efficiently.

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Answer 1

Here's one way to do it.

In [3]: df
Out[3]:
  string
0   abcd
1  abcde

In [4]: df['len'] = df['string'].str.len()

In [5]: df
Out[5]:
  string  len
0   abcd    4
1  abcde    5

Answer 2

Pandas has a vectorised string method for this: str.len(). To create the new column you can write:

df['char_length'] = df['string'].str.len()

For example:

>>> df
  string
0   abcd
1  abcde

>>> df['char_length'] = df['string'].str.len()
>>> df
  string  char_length
0   abcd            4
1  abcde            5

This should be considerably faster than looping over the DataFrame with a Python for loop.

Many other familiar string methods from Python have been introduced to Pandas. For example, lower (for converting to lowercase letters), count for counting occurrences of a particular substring, and replace for swapping one substring with another.