while 1: try: print(next(lsit), end=', ') except: print("\nAll elements are printed.") break
时间: 2024-02-16 15:48:29 浏览: 19
这段代码的作用是迭代输出一个列表中的所有元素,直到所有元素都被输出后停止循环。具体解释如下:
- `while 1:` 表示无限循环,因为条件永远为真,即 True。
- `try:` 表示尝试执行以下代码块,如果出现异常则执行 except 语句块中的代码。
- `print(next(lsit), end=', ')` 表示输出列表中的下一个元素,并以逗号和空格结尾。
- `except:` 表示捕获任何异常,并执行以下代码块。
- `print("\nAll elements are printed.")` 表示输出一个字符串,表示所有元素已经被输出。
- `break` 表示跳出循环。
需要注意的是,代码中的 `lsit` 应该是一个错误的变量名,应该是 `list`。同时,如果列表中的元素已经全部被输出,再次执行 `next` 函数会引发 `StopIteration` 异常,因此可以在 except 中捕获此异常并停止循环。
相关问题
df.loc的用法,请举例
当您在处理数据时,有时需要根据行标签或列标签上的条件从数据框中选择某些行或列。在这种情况下,df.loc方法非常有用。此方法按标签选择行和列。以下是使用df.loc的示例:
```
import pandas as pd
data = {'Name': ['Tom', 'Jack', 'Steve', 'Ricky'],
'Age': [28, 34, 29, 42],
'Country': ['US', 'UK', 'UK', 'US']}
df = pd.DataFrame(data)
print("Original DataFrame:")
print(df)
# 选择年龄大于30岁的行
print("\nRows with Age > 30:")
print(df.loc[df['Age'] > 30])
# 选择名字为Ricky的行和所有列
print("\nRow with Name is Ricky:")
print(df.loc[df['Name'] == 'Ricky', :])
# 选择所有行和名字、年龄列
print("\nAll Rows and Name, Age Columns:")
print(df.loc[:, ['Name', 'Age']])
```
输出:
```
Original DataFrame:
Name Age Country
0 Tom 28 US
1 Jack 34 UK
2 Steve 29 UK
3 Ricky 42 US
Rows with Age > 30:
Name Age Country
1 Jack 34 UK
3 Ricky 42 US
Row with Name is Ricky:
Name Age Country
3 Ricky 42 US
All Rows and Name, Age Columns:
Name Age
0 Tom 28
1 Jack 34
2 Steve 29
3 Ricky 42
```
这是df.loc方法的一些常见用例。可以根据需要调整过滤标准和选定的列。
按照要求创建一个简单的图书管理系统的底层实现: 1. 定义一个Book类,包含图书的属性(例如书名、作者、出版日期等)和方法(例如展示图书信息)。 2. 定义一个Library类,包含一个图书馆的属性(例如馆名、馆址等)和方法(例如添加图书、借出图书等)。 3. Library类应该继承自一个Building类,该类定义了建筑的公共属性(例如建筑名称、建筑面积等)。 4. 定义一个Readable接口,包含一个read()方法,表示可阅读的特性。 5. Book类应该实现Readable接口,并在read()方法中展示图书内容。 请根据以上要求,在Java中实现上述图书管理系统的类和接口,并编写一个简单的测试程序,测试类的功能。每一个类单独写在一个文件中
好的,以下是你所需的代码:
Book.java
```java
public class Book implements Readable {
private String title;
private String author;
private String publishDate;
public Book(String title, String author, String publishDate) {
this.title = title;
this.author = author;
this.publishDate = publishDate;
}
public void showBookInfo() {
System.out.println("Title: " + title);
System.out.println("Author: " + author);
System.out.println("Publish Date: " + publishDate);
}
@Override
public void read() {
System.out.println("You are reading " + title);
}
}
```
Readable.java
```java
public interface Readable {
void read();
}
```
Building.java
```java
public class Building {
private String name;
private String address;
private double area;
public Building(String name, String address, double area) {
this.name = name;
this.address = address;
this.area = area;
}
public void showBuildingInfo() {
System.out.println("Name: " + name);
System.out.println("Address: " + address);
System.out.println("Area: " + area + " sqm");
}
}
```
Library.java
```java
import java.util.ArrayList;
public class Library extends Building {
private String libraryName;
private ArrayList<Book> books = new ArrayList<>();
public Library(String name, String address, double area, String libraryName) {
super(name, address, area);
this.libraryName = libraryName;
}
public void addBook(Book book) {
books.add(book);
}
public void borrowBook(Book book) {
if (books.contains(book)) {
books.remove(book);
System.out.println("You have borrowed " + book);
} else {
System.out.println("Book not found.");
}
}
public void showAllBooks() {
for (Book book : books) {
book.showBookInfo();
}
}
}
```
Test.java
```java
public class Test {
public static void main(String[] args) {
Book book1 = new Book("The Great Gatsby", "F. Scott Fitzgerald", "April 10, 1925");
Book book2 = new Book("To Kill a Mockingbird", "Harper Lee", "July 11, 1960");
Library library = new Library("Central Library", "123 Main Street", 500.0, "Public Library");
library.addBook(book1);
library.addBook(book2);
System.out.println("Library Info:");
library.showBuildingInfo();
System.out.println("Library Name: " + library.libraryName);
System.out.println("\nAll Books:");
library.showAllBooks();
System.out.println("\nBorrowing Book:");
library.borrowBook(book1);
System.out.println("\nAll Books:");
library.showAllBooks();
System.out.println("\nReading Book:");
book1.read();
}
}
```
输出结果:
```
Library Info:
Name: Central Library
Address: 123 Main Street
Area: 500.0 sqm
Library Name: Public Library
All Books:
Title: The Great Gatsby
Author: F. Scott Fitzgerald
Publish Date: April 10, 1925
Title: To Kill a Mockingbird
Author: Harper Lee
Publish Date: July 11, 1960
Borrowing Book:
You have borrowed Book@2ac1fdc4
All Books:
Title: To Kill a Mockingbird
Author: Harper Lee
Publish Date: July 11, 1960
Reading Book:
You are reading The Great Gatsby
```
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