Úvod do iterace pandas DataFrame
Psaní efektivního kódu v Pythonu
Logan Thomas
Scientific Software Technical Trainer, Enthought
Shrnutí pandas
- Přehled pandas v kurzu Intermediate Python
- Knihovna pro analýzu dat
- Hlavní datová struktura je DataFrame
- Tabulková data s pojmenovanými řádky a sloupci
- Postavena na struktuře pole NumPy
- Cíl kapitoly:
- Osvědčené postupy pro iteraci přes pandas DataFrame
Baseballová statistika
import pandas as pd
baseball_df = pd.read_csv('baseball_stats.csv')
print(baseball_df.head())
Team League Year RS RA W G Playoffs
0 ARI NL 2012 734 688 81 162 0
1 ATL NL 2012 700 600 94 162 1
2 BAL AL 2012 712 705 93 162 1
3 BOS AL 2012 734 806 69 162 0
4 CHC NL 2012 613 759 61 162 0
Baseballová statistika
Team
0 ARI
1 ATL
2 BAL
3 BOS
4 CHC
Baseballová statistika
Team League Year RS RA W G Playoffs
0 ARI NL 2012 734 688 81 162 0
1 ATL NL 2012 700 600 94 162 1
2 BAL AL 2012 712 705 93 162 1
3 BOS AL 2012 734 806 69 162 0
4 CHC NL 2012 613 759 61 162 0
Výpočet procenta výher
import numpy as np
def calc_win_perc(wins, games_played):
win_perc = wins / games_played
return np.round(win_perc,2)
win_perc = calc_win_perc(50, 100)
print(win_perc)
0.5
Přidání procenta výher do DataFrame
win_perc_list = []for i in range(len(baseball_df)): row = baseball_df.iloc[i]wins = row['W'] games_played = row['G']win_perc = calc_win_perc(wins, games_played)win_perc_list.append(win_perc)baseball_df['WP'] = win_perc_list
Přidání procenta výher do DataFrame
print(baseball_df.head())
Team League Year RS RA W G Playoffs WP
0 ARI NL 2012 734 688 81 162 0 0.50
1 ATL NL 2012 700 600 94 162 1 0.58
2 BAL AL 2012 712 705 93 162 1 0.57
3 BOS AL 2012 734 806 69 162 0 0.43
4 CHC NL 2012 613 759 61 162 0 0.38
Iterace pomocí .iloc
%%timeit
win_perc_list = []
for i in range(len(baseball_df)):
row = baseball_df.iloc[i]
wins = row['W']
games_played = row['G']
win_perc = calc_win_perc(wins, games_played)
win_perc_list.append(win_perc)
baseball_df['WP'] = win_perc_list
183 ms ± 1.73 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
Iterace pomocí .iterrows()
win_perc_list = [] for i,row in baseball_df.iterrows():wins = row['W'] games_played = row['G'] win_perc = calc_win_perc(wins, games_played) win_perc_list.append(win_perc) baseball_df['WP'] = win_perc_list
Iterace pomocí .iterrows()
%%timeit
win_perc_list = []
for i,row in baseball_df.iterrows():
wins = row['W']
games_played = row['G']
win_perc = calc_win_perc(wins, games_played)
win_perc_list.append(win_perc)
baseball_df['WP'] = win_perc_list
95.3 ms ± 3.57 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
Procvičte iteraci DataFrame pomocí .iterrows()
Psaní efektivního kódu v Pythonu
