[英]How to remove strings that contain letters from a list?
I have a list containing strings with both letters, characters and and numbers:我有一个包含字母、字符和数字的字符串的列表:
list = ['hello', '2U:', '-224.3', '45.1', 'SA 2']
I want to only keep the numbers in a list and convert them to float
values.我只想将数字保留在列表中并将它们转换为
float
值。 How can I do that?我怎样才能做到这一点? I want the list to look like this:
我希望列表如下所示:
list = ['-224.3'. '45.1']
The list is created, when I do a serial.readline() from a Arduino, which gives me a string comprised of commands and data points.当我从 Arduino 执行 serial.readline() 时,会创建该列表,它为我提供了一个由命令和数据点组成的字符串。 So i looked like this:
所以我看起来像这样:
'hello,2U:,-224.3,45.1,SA 2'
I did a list.split(delimiter=',') and wanted to only have the data points for future calculations.我做了一个 list.split(delimiter=',') 并且只想拥有用于未来计算的数据点。
Probably the best way to see whether a string can be cast to float
is to just try
to cast it.查看是否可以将字符串强制转换为
float
的最佳方法可能是try
进行强制转换。
res = []
for x in lst:
try:
res.append(float(x))
except ValueError:
pass
Afterwards, res
is [-224.3, 45.1]
之后,
res
为[-224.3, 45.1]
You could also make this a list comprehension, something like [float(x) for x in lst if is_float(x)]
, but for this you will need a function is_float
that will essentially do the same thing: Try to cast it as float and return True, otherwise return False.你也可以将这个列表理解,像
[float(x) for x in lst if is_float(x)]
,但对于这一点,你需要一个功能is_float
,将基本上做同样的事情:尝试将它转换为浮动并返回 True,否则返回 False。 If you need this just once, the loop is shorter.如果您只需要一次,循环会更短。
You can try something like below -您可以尝试以下操作 -
def isNum(s):
try:
float(s)
return True
except ValueError:
return False
lst = ['hello', '2U:', '-224.3', '45.1', 'SA 2']
bools = list(map(lst,isNum))
deleted = 0
for idx, val in enumerate(bools):
if val:
continue
else:
del lst[idx-deleted]
deleted = deleted + 1
EDIT:编辑:
Or you can use或者你可以使用
def isNum(s):
try:
float(s)
return True
except ValueError:
return False
lst = ['hello', '2U:', '-224.3', '45.1', 'SA 2']
lst = list(filter(isNum, lst))
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