如果语句在列表中查找年龄

Question

我做了三个输入（名字、姓氏和年龄）并将它们放入一个文件中。最后一部分是如果年龄超过 18 岁，则使用此信息打印出某人的输入。我曾尝试使用字典，但不知何故我做错了。我可以使用列表或文件吗？我该怎么做才能使用使用该年龄的 if 语句来确定是否应打印详细信息。示例如下。

def details():
    c = input('Press 1 to enter details, press 2 to browse users or press 3 to check age')
    if c == '1':
        firstname = input('Please enter your firstname')
        surname = input('Please enter your surname')
        age = input('Please enter your age')
        myfile=open('details.txt', 'at')
        myfile.write(firstname + '\n')
        myfile.write(surname + '\n')
        myfile.write(age + '\n')
        myfile.close()
        detail2 = {'Fname': firstname, 'Sname': surname, 'Age': age}
        details()
    elif c == '2':
        detail2 = {'Fname': firstname, 'Sname': surname, 'Age': age}
        read()
    elif c == '3':
        detail2 = {'Fname': firstname, 'Sname': surname, 'Age': age}
        read18()
    else:
        details()
def read():
    myfile=open('details.txt', 'rt')
    x = myfile.read()
    print(x)
def read18():
    for item in detail2:
        if Age> 18:
            print('Over 18') 
        elif Age< 18:
            print('Under 18')
"""I need to know what to do so this will print the details. Just using over or under 18 as a starting point"""

details()

Answer 1

您试图在 read18() 中使用局部变量 detail2，但它超出了范围。您可能希望打开文件并读取现有详细信息以评估您的“if”循环条件。

Answer 2

好的，我认为您的代码可以进行一些改进。

1. 如果你继续调用 details()，你最终会达到允许的最大递归的限制。为此，您可以将代码放入 while True: 循环并调用 break 来中断它
2. input() 返回一个字符串，但年龄通常是一个数字(integer)，因此最好使用int() 将字符串转换为整数。可以直接在input() -> age = int(input('Please enter your age: '))上使用
3. 既然您有一个list 用户，您应该使用list 来跟踪他们。如果每个用户都有名字、姓氏和年龄，您调用使用字典来保存每个用户的数据，然后将此字典添加到您的所有用户列表中
4. 对于写入/读取文件，Python 有一个内置的 with 语句，它将为您关闭文件
5. 如果要快速保存列表/字典，可以使用 JSON

如果您将使用所有这些建议，您可以获得类似于此的代码：

import json

FILE_SAVEFILE = "details.json"

list_persons = []  # list with user's data

def data_save():
    """
    Saves user's data into FILE_SAVEFILE
    """
    with open(FILE_SAVEFILE, 'wt') as f:
        json.dump(list_persons, f)

def data_load():
    """
    Loads data into list_persons from FILE_SAVEFILE
    """
    global list_persons
    with open(FILE_SAVEFILE, 'rt') as f:
        list_persons = json.load(f)

while True:
    c = input('Press 1 to enter details, press 2 to browse users or press 3 to check age: ')
    if c == "1":
        new_person_data = {
            "firstname": input('Please enter your firstname: '),
            "surname": input('Please enter your surname: '),
            "age": int(input('Please enter your age: ')),
        }
        list_persons.append(new_person_data)
        data_save()
        continue
    if c == "2":
        data_load()
        for dict_user in list_persons:
            print('Firstname: ' + dict_user["firstname"])
            print('Surname: ' + dict_user["surname"])
            print('Age: ' + str(dict_user["age"]))
        continue
    if c == "3":
        for dict_user in list_persons:
            str_agestr = " is over 18" if dict_user["age"] > 18 else " is under 18"
            print(dict_user["firstname"] + " " + dict_user["surname"] + str_agestr)
        continue

Answer 3

可以对您的代码进行许多改进，实际上 E. Aho 的答案使用了其中的一些，但如果您是 python 新手，它们可能会有点令人困惑。 稍微调整你的代码并添加一些 cmets：

def details():
    c = input('Press 1 to enter details, press 2 to browse users or press 3 to check age: ')
    if c == '1':
        firstname = input('Please enter your firstname: ')
        surname = input('Please enter your surname: ')
        age = input('Please enter your age: ')
        myfile=open('details.txt', 'at')

        # write data as a single record

        myfile.write(firstname + ',' + surname + ',' + age + '\n')
        myfile.close()
        details()

    elif c == '2':
        read()
    elif c == '3':
        read18()
    else:
        details()

def read():
    myfile=open('details.txt', 'r')

    # read file line by line

    x = myfile.readlines()
    for item in x:
        print (item.strip()) #Strip newline
    myfile.close()

def read18():
    myfile=open('details.txt', 'r')
    x = myfile.readlines()
    for item in x:

        # split each line into component parts, splitting on comma separator and strip newline

        firstname,surname,age = item.strip().split(',')
        detail2 = {'Fname': firstname, 'Sname': surname, 'Age': int(age)}
        if detail2['Age'] > 17:
            print('Over 18 via Dict')
        else:
            print('Under 18 via Dict')

        # or dispense with the dictionary

        if int(age) > 17:
            print(firstname,surname,'at',age,'is 18 or over')
        else:
            print(firstname,surname,'at',age,'is under 18')
    myfile.close()
"""I need to know what to do so this will print the details. Just using over or under 18 as a starting point"""

details()