Add a column in a pandas df with a repeated sequence of values

Question

I want to add a column to a pandas DataFrame that has a sequence of int or even str.

This is the pandas DataFrame:

import pandas as pd

df = [{"us": "t1"},
{"us": "t2"},
{"us": "t3"},
{"us": "t4"},
{"us": "t5"},
{"us": "t6"},
{"us": "t7"},
{"us": "t8"},
{"us": "t9"},
{"us": "t10"},
{"us": "t11"},
{"us": "t12"}
    ]
df = pd.DataFrame(df)
df

I just want to add a column of a list of int or str like these:

list_int = [1, 2, 3, 4]

list_str = ['one','two','three','four']

Of course the code df['list_int']=list_int is not working because of the length.

The output should be this:

    us   list_int  list_str
0   t1      1        one
1   t2      2        two
2   t3      3        three
3   t4      4        four
4   t5      1        one
5   t6      2        two
6   t7      3        three
7   t8      4        four
8   t9      1        one
9   t10     2        two
10  t11     3        three
11  t12     4        four

Quang Hoang · Accepted Answer · 2019-08-01 17:47:13Z

4

You can use np.tile:

df['list_int'] = np.tile(list_int, len(df)//len(list_int) + 1)[:len(df)]

or simply

df['list_int'] = np.tile(list_int, len(df)//len(list_int)]

if len(df) is divisible by len(list_int).

answered Aug 1, 2019 at 17:47

Quang Hoang

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3 Comments

anky Over a year ago

can we look at tile with np.column_stack((list_int,list_str)) ? to get both columns repeated? I am unaware how to tile a 2D array

Quang Hoang Over a year ago

@anky_91 np.tile(np.array([list_int, list_str]), 2) works as expected.

anky Over a year ago

Thanks so totally np.column_stack(np.tile(np.array([list_int, list_str]), len(df))) :)

BENY · Accepted Answer · 2019-08-01 17:58:18Z

1

Let us do something new np.put

df['list_int']=''
df['list_str']=''
np.put(df.list_str,np.arange(len(df)),list_str)
np.put(df.list_int,np.arange(len(df)),list_int)


df
Out[83]: 
     us list_int list_str
0    t1        1      one
1    t2        2      two
2    t3        3    three
3    t4        4     four
4    t5        1      one
5    t6        2      two
6    t7        3    three
7    t8        4     four
8    t9        1      one
9   t10        2      two
10  t11        3    three
11  t12        4     four

answered Aug 1, 2019 at 17:58

BENY

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Comments

Raphael · Accepted Answer · 2019-08-01 17:53:28Z

0

multiplying lists with a number n repeats the list n times.

2 * ['one', 'two', 'three']

equals

['one', 'two', 'three', 'one', 'two', 'three']

so if you data frame is df you and your snippet is s=['one', 'two', 'three'] you can build your column like this:

col = (len(df) % len(s)) * s + s[:int(len(df) / len(s))]

edited Aug 1, 2019 at 17:53

answered Aug 1, 2019 at 17:48

Raphael

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Comments

Paulfryy · Accepted Answer · 2019-08-01 18:04:02Z

0

Try this - might not be the best universal option but it works...

df["list_str"]=np.array(list_str)[df["us"].index.values%4]
df["list_int"]=np.array(list_int)[df["us"].index.values%4]

output


    us  list_str    list_int
0   t1  one         1
1   t2  two         2
2   t3  three       3
3   t4  four        4
4   t5  one         1
5   t6  two         2
6   t7  three       3
7   t8  four        4
8   t9  one         1
9   t10 two         2
10  t11 three       3
11  t12 four        4

answered Aug 1, 2019 at 18:04

Paulfryy

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