python中for循环中的if语句

Question

我有一个字符串列表要遍历，每行包含'is connected to' 或'likes to play' 作为标记，列表的每个项目中只有一个。所以我使用了一个for循环来迭代列表，里面是if语句来决定哪个短语在项目中。字符串列表是这样的：

lines = ['a is connected to b','a likes to play guitar, trampolines','b is connected to m,z', 'b likes to play piano','c is connected to s','c likes to play video games, ball games']

def create(string_input):
    network = {}
    lines = string_input.split('.')
    for line in lines:
        user = {}
        if len(line)>0:
            name = line[0:line.index(' ')]
            if 'is connected to' in line:
                friends = line[line.index('is connected to')+len('is connected to')+1:].split(",")
                user['friends']= friends
            elif 'likes to play' in line: 
                likes = line[line.index('likes to play')+ len('likes to play')+1:].split(",")
                user['likes']= likes
            network[name] = user
    return network
print create(lines)

但是，打印的结果并没有给我user['friends'] 和user['likes'] 最终结果仅包含第二个 if 块中的数据，并且所有 if 'is connected to' 数据都被替换为 [] 并丢失。我不确定数据结构或 if 语句是否处理不正确。任何人都可以帮我看看这里有什么问题吗？提前致谢。

编辑

正如 David 所指出的，代码中的问题在于更新字典而不是 for 和 if 语句。谢谢大家！！

Answer 1

试试这个：

lines = ['a is connected to b','a likes to play guitar, trampolines','b is connected to m,z', 'b likes to play piano','c is connected to s','c likes to play video games, ball games']

def create(string_input):
    network = {}
    lines = string_input.split('.')
    for line in lines:
        user = {}
        if len(line)>0:
            name = line[0:line.index(' ')]
            if 'is connected to' in line:
                friends = line[line.index('is connected to')+len('is connected to')+1:].split(",")
                user['friends']= friends
            elif 'likes to play' in line: 
                likes = line[line.index('likes to play')+ len('likes to play')+1:].split(",")
                user['likes']= likes
            network[name] = user
    return network

for line in lines:
    print(create(line))

您的代码很好，您只需逐项传递行列表中的字符串。还有其他方法可以做到这一点，但这是一种简单的方法。

希望对你有帮助！

编辑

我将迭代放在主函数中，因为当我提交原始答案时，我可以听到我的 CS 教授痛苦地尖叫。

def create(string_input):
    network = {}
    lines = string_input.split('.')
    for line in lines:
        user = {}
        if len(line)>0:
            name = line[0:line.index(' ')]
            if 'is connected to' in line:
                friends = line[line.index('is connected to')+len('is connected to')+1:].split(",")
                user['friends']= friends
            elif 'likes to play' in line: 
                likes = line[line.index('likes to play')+ len('likes to play')+1:].split(",")
                user['likes']= likes
            network[name] = user
    return network

def main():
    originalStrings = ['a is connected to b','a likes to play guitar, trampolines','b is connected to m,z', 'b likes to play piano','c is connected to s','c likes to play video games, ball games']
    for string in originalStrings:
        print(create(string))
main()

Answer 2

network[name] = user 行是问题所在。看输入线'a 连接到 b'，'a 喜欢弹吉他，蹦床'。处理第一行时，清空user 变量并将连接写入它，然后将network[name] 设置为等于user。然后在处理第二行时，再次清空user 变量并将喜欢的值写入其中，然后将network[name] 设置为等于（新的）user，破坏之前存在于network[name] 中的任何内容。因此，您只需要保留每个用户的最后一行。

要解决此问题，请将network[name] = user 替换为：

if name in network:
    network[name].update(user)
else:
    network[name] = user

Answer 3

你每次在循环中替换dict用户，而dict会丢失之前的信息。试试这个：

def create(string_input):
    network = {}
    lines = string_input.split('.')
    for line in lines:
        if len(line)>0:
            name = line[0:line.index(' ')]
            if name not in network:
                network[name] = {}
            if 'is connected to' in line:
                friends = line[line.index('is connected to')+len('is connected to')+1:].split(",")
                network[name]['friends']= friends
            elif 'likes to play' in line: 
                likes = line[line.index('likes to play')+ len('likes to play')+1:].split(",")
                network[name]['likes']= likes

    return network