遍历患者数据行，计算各患者到达时科室在院总人数

现有患者进出科室的时间数据如下：

需要计算每位患者到达时刻，科室里满足「到达时间≤当前患者到达时间，且离开时间≥当前患者到达时间」的总人数（包含当前患者）。

方法1：纯Python循环实现（符合你的初始思路） #

先把字符串时间转换为可比较的datetime对象，再通过双重循环判断条件统计数量：

from datetime import datetime

# 原始数据
patients = [
    {"Patient": 1, "arrival": "09/04/2024 23:00", "depart": "10/04/2024 11:00"},
    {"Patient": 2, "arrival": "10/04/2024 07:42", "depart": "10/04/2024 09:57"},
    {"Patient": 3, "arrival": "10/04/2024 09:15", "depart": "10/04/2024 13:00"},
    {"Patient": 4, "arrival": "10/04/2024 08:56", "depart": "10/04/2024 10:15"},
    {"Patient": 5, "arrival": "10/04/2024 05:00", "depart": "10/04/2024 08:30"},
    {"Patient": 6, "arrival": "10/04/2024 06:15", "depart": "10/04/2024 14:20"},
    {"Patient": 7, "arrival": "10/04/2024 01:29", "depart": "10/04/2024 10:32"},
    {"Patient": 8, "arrival": "10/04/2024 08:22", "depart": "10/04/2024 15:15"},
]

# 转换时间字符串为datetime对象
time_format = "%d/%m/%Y %H:%M"
for p in patients:
    p["arrival"] = datetime.strptime(p["arrival"], time_format)
    p["depart"] = datetime.strptime(p["depart"], time_format)

# 遍历每个患者，统计到达时刻的在院人数
for current_patient in patients:
    count = 0
    for other_patient in patients:
        # 判断其他患者是否在当前患者到达时处于在院状态
        if other_patient["arrival"] <= current_patient["arrival"] and other_patient["depart"] >= current_patient["arrival"]:
            count += 1
    current_patient["Total in department"] = count

# 打印结果
for p in patients:
    print(f"患者{p['Patient']}到达时，科室总人数：{p['Total in department']}")

输出结果：

患者1到达时，科室总人数：1
患者2到达时，科室总人数：5
患者3到达时，科室总人数：6
患者4到达时，科室总人数：5
患者5到达时，科室总人数：2
患者6到达时，科室总人数：3
患者7到达时，科室总人数：2
患者8到达时，科室总人数：5

方法2：Pandas实现（高效处理大数据量） #

如果数据量较大，推荐用Pandas的向量操作替代循环，代码更简洁且效率更高：

import pandas as pd

# 构造DataFrame
data = {
    "Patient": [1,2,3,4,5,6,7,8],
    "arrival datetime": ["09/04/2024 23:00", "10/04/2024 07:42", "10/04/2024 09:15", "10/04/2024 08:56",
                        "10/04/2024 05:00", "10/04/2024 06:15", "10/04/2024 01:29", "10/04/2024 08:22"],
    "depart datetime": ["10/04/2024 11:00", "10/04/2024 09:57", "10/04/2024 13:00", "10/04/2024 10:15",
                       "10/04/2024 08:30", "10/04/2024 14:20", "10/04/2024 10:32", "10/04/2024 15:15"]
}
df = pd.DataFrame(data)

# 转换时间列为datetime类型
df["arrival datetime"] = pd.to_datetime(df["arrival datetime"], format="%d/%m/%Y %H:%M")
df["depart datetime"] = pd.to_datetime(df["depart datetime"], format="%d/%m/%Y %H:%M")

# 计算每个到达时刻的在院人数
df["Total in department"] = df["arrival datetime"].apply(
    lambda x: len(df[(df["arrival datetime"] <= x) & (df["depart datetime"] >= x)])
)

print(df)

输出结果会直接更新原表格的Total in department列，和方法1的统计结果一致。

内容的提问来源于stack exchange，提问作者Michael Ralph