1. For loop的执行顺序 参考:https://kelepython.readthedocs.io/zh/latest/c01/c01_10.html#for For loop是一个遍历命令,意味着要把一个序列里的所有元素都循环一遍。 Python执行for loop从第一行到最后一行,exp: for question in questions: print("---") print(question) for option in options[question...
导读:赋值表达式(assignment expression)是Python3.8新引入的语法,它会用到海象操作符(walrus operator)。这种写法可以解决某些持续已久的代码重复问题。a = b是一条普通的赋值语句,读作a equals b,而a := b则是赋值表达式,读作a walrus b。 这个符号为什么叫walrus呢?因为把:=顺时针旋转90°之后,冒号就是海象...
for fruit, count in fresh_fruit.items(): batch = make_juice(fruit, count) bottles.extend(batch) print(bottles) 有了海象操作符,就不需要使用loop-and-a-half模式了,我们可以在每轮循环的开头给fresh_fruit变量赋值,并根据变量的值来决定要不要继续循环。这个写法简单易读,所以应该成为首选方案。 FRUIT_T...
第3 行: 使用海象运算符将值 True 赋给 walrus。 在上面的“walrus”变量中,我们可以看到两种赋值类型之间有一个微妙但重要的区别。海象运算符返回值,而传统赋值不返回值。在第 1 行的 “walrus = False” 之后,没有打印任何值,而在第 3 行的海象运算符表达式之后,则打印出了 True。 从这个例子中,我们可以...
loop 不仅是if,循环的条件也可以用到walrus operator。比如下面这段代码 while True: cmd = input() if cmd == "exit": break print(f"Got input {cmd}") 用一个循环不断从用户读取命令。如果命令是exit就退出循环。如果是其它命令就打印出来。改用walrus运算符就可以写成这样 ...
Without the walrus operator, we have to create two lines. Python walrus read input In the following example, we use the walrus operator in a while loop. read_words.py #!/usr/bin/python words = [] while (word := input("Enter word: ")) != "quit": ...
Python's := operator is often called the "walrus operator" because it looks like a walrus on its side (note the tusks). This operator was added in Python 3.8. For more, see Python's walrus operator. Comment Programmers add comments to their code to explain something that may not be app...
One design principle underpinning the walrus operator is that there are no identical code contexts where both an assignment statement using the = operator and an assignment expression using the := operator would be valid. For example, you can’t do a plain assignment with the walrus operator:...
下面就一些明显的新功能,进行说明。 Assignment Expressions 又叫做「海象运算符」(The Walrus Operator)。因为:=很像海象「眼睛小,长着两枚长长的牙」。 Python Positional-Only parameters 说白了就是强制使用者用位置参数 具体的
A common use case for the walrus operator is to simplify code where a variable would normally need to be defined before being used, such as in some conditional statements. Consider the followingwhileloop: importrandom value=random.randint(1,20)whilevalue<18:print(value)value=random.randint(1,...