Python - for循环，执行一个总和并在新列中存储答案

Question

我想计算所有具有相同名称的人的总年龄：请参阅此处的示例表。

table with names

这是迄今为止我所编写的代码..但它是不完整的，这是行不通的..

final_df = DataFrame() 

for i in [list of names]: 
dummy = sort_df.loc[sort_df['name'] == i]  
total_age = 0 

for j in dummy.age:  
    age2 = dummy.age(j) 

    total_age = total_age + age2 

    final_df.append(total_age) 


final_df['total_age'] = total_age 

我该如何解决这个问题，我可以写一个代码可以迭代多个具有相同名称的人并将它们相加并将它们存储在一个新列中？

最后，它应该是这样的：

Result

Answer 1

在你的代码的样子，我假设有具有名为input.csv一个CSV文件已使用此数据读取到sort_df：

name,age,total age 
Alfredo,13, 
Alfredo,12, 
Alfredo,15, 
Jaap,12, 
Jaap,14, 
Koen,16, 
Lian,76, 
Lian,45, 
Lian,34, 
Lian,14, 

在这种情况下，不需要声明另一个dummy数据帧。使用此：

from pandas import DataFrame 

sort_df = DataFrame.from_csv("inCSV.txt", index_col=False) 
final_df = sort_df 

# Use a dictionary to keep track instead 
total_age = {} 
for name in sort_df["name"]: 
    if name not in total_age.keys(): 
     total_age[name] = 0 

# Add up the ages 
for index in xrange(len(sort_df)): 
    person = sort_df.loc[index] 
    name = person["name"] 
    age = person["age"] 
    total_age[name] += age 

# Set the new ages into final_df 
for index in xrange(len(final_df)): 
    person = final_df.loc[index] 
    name = person["name"] 
    final_df.set_value(index, "total age", total_age[name]) 

print final_df 

，这将给你（在final_df）：

 name age total age 
0 Alfredo 13  40.0 
1 Alfredo 12  40.0 
2 Alfredo 15  40.0 
3  Jaap 12  26.0 
4  Jaap 14  26.0 
5  Koen 16  16.0 
6  Lian 76  169.0 
7  Lian 45  169.0 
8  Lian 34  169.0 
9  Lian 14  169.0 

Answer 2

你在这里找到了答案：

from collections import defaultdict 
list_name = [ 
{'age': 25, 'name': 'alfredo'}, 
{'age': 44, 'name': 'alfredo'}, 
{'age': 23, 'name': 'jaap'}, 
{'age': 60, 'name': 'jaap'} 
] 

k={} 
c = defaultdict(int) 
for d in list_name: 
    c[d['name']] += d['age'] 
    k[d['name']] = c[d['name']] 
for d in list_name: 
    d['total_age'] = k[d['name']] 
print list_name 

Answer 3

数据。例如，

name,age 
Alfredo,13, 
Alfredo,12, 
Alfredo,15, 
Jaap,12, 
Jaap,14, 
Koen,16, 
Lian,76, 
Lian,45, 
Lian,34, 
Lian,14, 

import csv 
from collections import defaultdict 
result = defaultdict(int) 
reader = csv.DictReader(csv_file_handle) 
for person in reader: 
    name = person['name'].lower() 
    age = int(person['age']) 
    result[name] += age 
>>> result 
defaultdict(int, {'alfredo': 40, 'jaap': 26, 'koen': 16, 'lian': 169}) 

要更新result

# make a reader object  
# make a writer object with fieldnames ['name', 'age', 'total_age'] 
# write header 
for person in reader: 
    person.update({'total_age': result[person['name'].lower()]}) 
    writer.writerow(person)