Question

我想检查字符串是否在列表中并检查它是否也不在列表中：

supplies = ['pens','staplers','flame-throwers','binders']    

m = ['pens','a']
b = ['',not]

for x  in range(len(m)):
    for j in range(len(b)): 
        print(m[x] , b[j] , m[x] + b[j] in supplies)

但是我遇到语法错误：

b = ['',not]

如果我将其更改为：

b = ['','not']

然后它没有运行该操作并且说没有供应品是假的，这是不正确的。

如何不输入列表b以便它作为运算符运行？

由于

Answer 1

如果我理解正确，您正试图找出m中的每个值是否在supplies中。试试这个：

supplies = ['pens','staplers','flame-throwers','binders']    
m = ['pens','a']

# this will iterate each item in the list m, no need to iterate over m indices in this case
for item in m:  
    print(item, item in supplies)

Answer 2

我认为这可能会做你想要实现的目标：

supplies = ['pens','staplers','flame-throwers','binders']    

m = ['pens','a']
b = [True,False] #True if we want to see if the element is in the list,
                 #False if we want to see if it is not in the list

for x  in range(len(m)):
    for j in range(len(b)): 
        print(m[x] , b[j] , b[j] == (m[x] in supplies))

或者，如果你无法控制b的格式，那就是一个稍微复杂的解决方案：

supplies = ['pens','staplers','flame-throwers','binders']    

m = ['pens','a']
b = ['','not']

for x  in range(len(m)):
    for j in range(len(b)): 
        print(m[x] , b[j] , (b[j]== 'not') != (m[x] in supplies))

Answer 3

您无法在列表中存储运算符。同样尝试#add an appropriately named package to the search() path attach(environment(), name = "package:pkg") #source the functions sys.source("test.R", envir = as.environment("package:pkg"))。它不起作用 - 操作员必须操作！

你做的是创建一个执行该操作的函数，并将其存储起来。

src

Answer 4

例如，您可以使用eval（）函数：

print(m[x], b[j], eval("'%s' %s in supplies" % (m[x], b[j])))

变量b应该是：

b = ['','not']

在列表中使用运算符

4 个答案: