Vectorization over Pandas series

Writing Efficient Code with pandas

Leonidas Souliotis

PhD Candidate

DataFrames as arrays

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How to perform pandas vectorization

start_time = time.time()
poker[['R1', 'R2', 'R3', 'R4', 'R5']].sum(axis=1)
print("Time using pandas vectorization: {} sec".format(time.time() - start_time))

Time using pandas vectorization: 0.0026819705 sec

poker[['R1', 'R2', 'R3', 'R4', 'R5']].sum(axis=1).head()

|              |    | 
|--------------|----| 
| 0            | 47 | 
| 1            | 47 | 
| 2            | 47 | 
| 3            | 47 | 
| 4            | 47 | 
| dtype: int64 | -- |

Comparison to the previous methods

data_generator = data.iterrows()

start_time = time.time()
for index, value in data_generator:
        sum([value[1], value[3], value[5], value[7]])
print("Time using .iterrows(){} seconds" % (time.time() - start_time))

Results from the above operation calculated in 3.37918996 seconds

start_time = time.time()
data[['R1', 'R2', 'R3', 'R4', 'R5']].apply(lambda x: sum(x),axis=1)
print("Results from the above operation calculated in %s seconds" % (time.time() - start_time))

Results from the above operation calculated in 0.637711048 seconds

- Difference between vectorization and the `.iterows()` function: 111,800.75%
- Difference between vectorization and the `.apply()` function: 20,853%

Let's do it!

Writing Efficient Code with pandas