Python 替换列表中的 None 值？
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Replace None value in list?
提问by user7172
I have:
我有：
d = [1,'q','3', None, 'temp']
I want to replace None value to 'None' or any string
我想将 None 值替换为 'None' 或任何字符串
expected effect:
预期效果：
d = [1,'q','3', 'None', 'temp']
a try replace in string and for loop but I get error:
尝试在字符串和 for 循环中替换，但出现错误：
TypeError: expected a character buffer object
采纳答案by Martijn Pieters
Use a simple list comprehension:
使用简单的列表理解：
['None' if v is None else v for v in d]
Demo:
演示：
>>> d = [1,'q','3', None, 'temp']
>>> ['None' if v is None else v for v in d]
[1, 'q', '3', 'None', 'temp']
Note the is Nonetest to match the Nonesingleton.
注意is None匹配None单例的测试。
回答by K DawG
Using a lengthy and inefficient however beginner friendlyfor loop it would look like:
使用冗长且低效但对初学者友好的for 循环，它看起来像：
d = [1,'q','3', None, 'temp']
e = []
for i in d:
if i is None: #if i == None is also valid but slower and not recommended by PEP8
e.append("None")
else:
e.append(i)
d = e
print d
#[1, 'q', '3', 'None', 'temp']
Only for beginners, @Martins answer is more suitable in means of power and efficiency
仅针对初学者，@Martins 的回答在功率和效率方面更适合
回答by Abhijit
List comprehension is the right way to go, but in case, for reasons best known to you, you would rather replace it in-place rather than creating a new list (arguing the fact that python list is mutable), an alternate approach is as follows
列表理解是正确的方法，但如果出于您最了解的原因，您宁愿就地替换它而不是创建新列表（认为 python 列表是可变的），另一种方法是跟随
d = [1,'q','3', None, 'temp', None]
try:
while True:
d[d.index(None)] = 'None'
except ValueError:
pass
>>> d
[1, 'q', '3', 'None', 'temp', 'None']
回答by Saullo G. P. Castro
You can simply use mapand convert all itemsto strings using the strfunction:
您可以使用以下函数简单地使用所有项目map并将其转换为字符串：str
map(str, d)
#['1', 'q', '3', 'None', 'temp']
If you only want to convert the Nonevalues, you can do:
如果您只想转换None值，您可以执行以下操作：
[str(di) if di is None else di for di in d]
回答by Uzzy
Starting Python 3.6 you can do it in shorter form:
从 Python 3.6 开始，您可以以更短的形式进行：
d = [f'{e}' for e in d]
hope this helps to someone since, I was having this issue just a while ago.
希望这对某人有所帮助，因为不久前我遇到了这个问题。
