计算大熊猫中每组以逗号分隔的字符串中的所有单词

Question

i would like to count schools(separated by commas) from the data frame given below.

Dataframe:

State    Counties    Schools_list
S1       C1          GradeA,GradeB,GradeC
S1       C1          GradeD
S2       C1          GradeA,GradeB
S2       C2          GradeC
S3       C2          GradeA,GradeB
S3       C3          GradeC,GradeD

Output:

State          Schools_count
S1             4
S2             3
S3             4

How to count comma separated list of schools from last column by State.

Answer 1

A simple solution here would be to count the commas:

df['Schools_list'].str.count(',').add(1).groupby(df.State).sum()

State
S1    4
S2    3
S3    4
Name: Schools_list, dtype: int64

Note that, once you have counted the commas, group on the State name to get the count by state.

As a DataFrame,

(df['Schools_list'].str.count(',')
                   .add(1)
                   .groupby(df.State)
                   .sum()
                   .reset_index(name='Schools_count'))

  State  Schools_count
0    S1              4
1    S2              3
2    S3              4

---

You can also split on comma and find the length of the lists created, but this is a bit slower.

df['Schools_list'].str.split(',+').str.len().groupby(df.State).sum()

State
S1    4
S2    3
S3    4
Name: Schools_list, dtype: int64