Pandas Series: str.zfill() function

Series-str.zfill() function

The str.zfill() function is used to pad strings in the Series/Index by prepending '0' characters.
Strings in the Series/Index are padded with '0' characters on the left of the string to reach a total string length width. Strings in the Series/Index with length greater or equal to width are unchanged.

Syntax:

Series.str.zfill(self, width)

Parameters:

Returns: Series/Index of objects

Example:

Python-Pandas Code:

import numpy as np
import pandas as pd
s = pd.Series(['-2', '2', '2000', 20, np.nan])
s

Output:

0      -2
1       2
2    2000
3      20
4     NaN
dtype: object

Note that 10 and NaN are not strings, therefore they are converted to NaN. The minus sign in '-2' is treated as a regular character and the zero is added to the left of it (str.zfill() would have moved it to the left). 2000 remains unchanged as it is longer than width.

Python-Pandas Code:

import numpy as np
import pandas as pd
s = pd.Series(['-2', '2', '2000', 20, np.nan])
s.str.zfill(3)

Output:

0     0-2
1     002
2    2000
3     NaN
4     NaN
dtype: object

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