Question

我知道外部for循环应该运行一次，而内部for循环应该完全运行，但是一旦内部for循环完成，外部for循环就不会再继续执行文件中的第二行。怎么了？

import csv
import pprint
import sys


team = []

with open("sample_runner_data.csv", "r") as sample_csv:
    sample_csv = csv.DictReader(sample_csv)
    for lines in sample_csv:
        theLine = lines["team"]
        for line in sample_csv:
            if(theLine == line["team"]):
                print(line["team"])
                team.append(line["time"])
'''
The output of the above print(line["team]) statement is as follows. Abra is simply the team 
name and there are 7 teams named Abra.

Abra
Abra
Abra
Abra
Abra
Abra
Abra
'''

Answer 1

您使用的是相同的基础sample_csv文件，这意味着一旦迭代遍历完，所有后续迭代器将结束。读入数据，然后执行循环：

with open("sample_runner_data.csv", "r") as sample_csv:
    sample_csv = csv.DictReader(sample_csv)
    data = list(sample_csv)

for lines in data:
    theLine = lines["team"]
    for line in data:
        if(theLine == line["team"]):
            print(line["team"])
            team.append(line["time"])

但是，如果您只是一直在寻找每个团队的聚会，这可能不是您想要的，例如：

data = {}
with open("sample_runner_data.csv", "r") as sample_csv:
    sample_csv = csv.DictReader(sample_csv)
    for line in sample_csv:
        data.setdefault(line['team'], []).append(line['time'])

现在data将包含team作为键，所有time作为值。

循环的文件读取嵌套不会多次循环

1 个答案: