python groupby count()
时间: 2023-08-29 09:12:48 浏览: 40
The groupby() function in Python is used to group the data based on a specific column. The count() function is used to count the number of occurrences of each group.
Here is an example of how to use groupby() and count() functions in Python:
```python
import pandas as pd
# create a sample dataframe
df = pd.DataFrame({'Name': ['John', 'Mary', 'John', 'Peter', 'Mary'],
'Age': [25, 35, 30, 45, 40],
'City': ['New York', 'Los Angeles', 'Chicago', 'Houston', 'Miami']})
# group by the 'Name' column and count the number of occurrences
count_df = df.groupby(['Name']).count()
print(count_df)
```
Output:
```
Age City
Name
John 2 2
Mary 2 2
Peter 1 1
```
In the above example, we have grouped the data by the 'Name' column and counted the number of occurrences of each name. The resulting dataframe shows the count for each name.