I have a list like string which I want to convert to a list, but so far I'm unlucky. The string is like follows:
my_string="[749385,435,'20/07/11 05:32','34035',1298,tmp_host_name,'312642',6577,tmp_guest_name,'-0.5,-1.0','2.5,3.0','9.5 ',tmp_league_name,'2' ,'0','0','0','4',' 2','0','1','0.0,-0.5','4.5','1.0',1]"
My problems are:
I can't use eval because some of the items in the list to be are not strings, so it gives me
eval(my_string)
>NameError: name 'tmp_host_name' is not defined
I can't use ast.literal_eval because again, it gives an error
ast.literal_eval(my_string)
>ValueError: malformed node or string: <_ast.Name object at 0x0000017E7DA9E488>
and I can't do it with strip and split because some of the items are like '2.5,3.0' and this is splitted as well, something I don't want
my_string.strip('][').split(',')
['749385','435',"'20/07/11 05:32'", "'34035'",'1298','tmp_host_name',"'312642'",'6577','tmp_guest_name',"'-0.5","-1.0'","'2.5","3.0'","'9.5','tmp_league_name', "'2' ","'0'","'0'","'0'","'4'","' 2'","'0'","'1'","'0.0","-0.5'","'4.5'","'1.0'",'1']
One possible route is to use my last approach and verify that every element has 2 ' characters, and if not, merge it with the following element, but I'm looking for something a little more pythonic.
newlist=list()
for el in k:
if el.startswith("'") and el.endswith("'"):newlist.append(el)
elif el.startswith("'"):
compound=el
elif el.endswith("'"):
compound+=el
newlist.append(compound)
else:newlist.append(el)
Problem is, if I do this, the resulting list loses its order and becomes useless
Thanks!
Related
I am quite new to python.
And i want to only get a certain format from a bigger list, example:
Whats in the list:
/ABC/EF213
/ABC/EF
/ABC/12AC4
/ABC/212
However the only on i want listed are the ones with this format /###/##### while the rest gets discarded
You could use a generator expression or a for loop to check each element of the list to see if it matches a pattern. One way of doing this would be to check if the item matches a regex pattern.
As an example:
import re
original_list = ["Item I don't want", "/ABC/EF213", "/ABC/EF", "/ABC/12AC4", "/ABC/212", "123/456", "another useless item", "/ABC/EF"]
filtered_list = [item for item in original_list if re.fullmatch("\/\w+\/\w+", item) is not None]
print(filtered_list)
outputs
['/ABC/EF213', '/ABC/EF', '/ABC/12AC4', '/ABC/212', '/ABC/EF']
If you need help making regex patterns, there are many great websites such as regexr which can help you
Every String can be used as a list without any conversion. If the only format you want to check is /###/##### then you can simply make if commands like these:
for text in your_list:
if len(text) == 10 and text[0] == "/" and text[4] == "/" (and so on):
print(text)
Of course this would require a lot of if statements and would take a pretty long time. So I would recomend doing a faster and simpler scan. We could perform this one by, for example, splitting the texts, which would look something like this:
for text in your_list:
checkstring = text.split("/")
Now you have your text Split in parts, and you can simply check what lengths these new parts have with the len() command.
I want to access the strings which are inside my list
my_list=['12:00','12:30','13:00','13:30','15:00','15:30']
I have tried the below code, however I am getting 1 and 1 as the answer.
for i,my_list in enumerate(my_list):
my_list_start=my_list[i]
my_list_end=my_list[i+1]
The expected result is:
I have to combine the two values from a list. For example,
my output should looks like :
[{"start":12:00,'end':12:30},{'start':12:30,'end':13:00},
{'start':13:00,'end':13:30},{'start':15:00,'end':15:30'}]
for i,my_list in enumerate(my_list): #my_list is refering the the string at i not my_list
my_list_start=my_list[i]
my_list_end=my_list[i+1]
You can't redefine the list that you are iterating over otherwise it will cause weird issues. In this case it is being redefined to a string and it is accessing the first number in that.
Do this instead:
for i,item in enumerate(my_list): # notice ``ITEM`` instead of my_list (we don't want to rename my_list)
my_list_start=my_list[i]
my_list_end=my_list[i+1]
Or don't even bother with enumeration:
for idx in range(my_list):
my_list_start= my_list[idx]
my_list_end=my_list[idx+1]
Then I am assuming you put it into a dictionary elsewhere because you don't really have any logic here to do that.
I have a List of Lists that looks like this (Python3):
myLOL = ["['1466279297', '703.0']", "['1466279287', '702.0']", "['1466279278', '702.0']", "['1466279268', '706.0']", "['1466279258', '713.0']"]
I'm trying to use a list comprehension to convert the first item of each inner list to an int and the second item to a float so that I end up with this:
newLOL = [[1466279297, 703.0], [1466279287, 702.0], [1466279278, 702.0], [1466279268, 706.0], [1466279258, 713.0]]
I'm learning list comprehensions, can somebody please help me with this syntax?
Thank you!
[edit - to explain why I asked this question]
This question is a means to an end - the syntax requested is needed for testing. I'm collecting sensor data on a ZigBee network, and I'm using an Arduino to format the sensor messages in JSON. These messages are published to an MQTT broker (Mosquitto) running on a Raspberry Pi. A Redis server (also running on the Pi) serves as an in-memory message store. I'm writing a service (python-MQTT client) to parse the JSON and send a LoL (a sample of the data you see in my question) to Redis. Finally, I have a dashboard running on Apache on the Pi. The dashboard utilizes Highcharts to plot the sensor data dynamically (via a web socket connection between the MQTT broker and the browser). Upon loading the page, I pull historical chart data from my Redis LoL to "very quickly" populate the charts on my dashboard (before any realtime data is added dynamically). I realize I can probably format the sensor data the way I want in the Redis store, but that is a problem I haven't worked out yet. Right now, I'm trying to get my historical data to plot correctly in Highcharts. With the data properly formatted, I can get this piece working.
Well, you could use ast.literal_eval:
from ast import literal_eval
myLOL = ["['1466279297', '703.0']", "['1466279287', '702.0']", "['1466279278', '702.0']", "['1466279268', '706.0']", "['1466279258', '713.0']"]
items = [[int(literal_eval(i)[0]), float(literal_eval(i)[1])] for i in myLOL]
Try:
import json
newLOL = [[int(a[0]), float(a[1])] for a in (json.loads(s.replace("'", '"')) for s in myLOL)]
Here I'm considering each element of the list as a JSON, but since it's using ' instead of " for the strings, I have to replace it first (it only works because you said there will be only numbers).
This may work? I wish I was more clever.
newLOL = []
for listObj in myLOL:
listObj = listObj.replace('[', '').replace(']', '').replace("'", '').split(',')
newListObj = [int(listObj[0]), float(listObj[1])]
newLOL.append(newListObj)
Iterates through your current list, peels the string apart into a list by replace un-wanted string chracters and utilizing a split on the comma. Then we take the modified list object and create another new list object with the values being the respective ints and floats. We then append the prepared newListObj to the newLOL list. Considering you want an actual set of lists within your list. Your previously documented input list actually contains strings, which look like lists.
This is a very strange format and the best solution is likely to change the code which generates that.
That being said, you can use ast.literal_eval to safely evaluate the elements of the list as Python tokens:
>>> lit = ast.literal_eval
>>> [[lit(str_val) for str_val in lit(str_list)] for str_list in myLOL]
[[1466279297, 703.0], [1466279287, 702.0], [1466279278, 702.0], [1466279268, 706.0], [1466279258, 713.0]]
We need to do it twice - once to turn the string into a list containing two strings, and then once per resulting string to convert it into a number.
Note that this will succeed even if the strings contain other valid tokens. If you want to validate the format too, you'd want to do something like:
>>> def process_str_list(str_list):
... l = ast.literal_eval(str_list)
... if not isinstance(l, list):
... raise TypeError("Expected list")
... str_int, str_float = l
... return [int(str_int), float(str_float)]
...
>>> [process_str_list(str_list) for str_list in myLOL]
[[1466279297, 703.0], [1466279287, 702.0], [1466279278, 702.0], [1466279268, 706.0], [1466279258, 713.0]]
Your input consists of a list of strings, where each string is the string representation of a list. The first task is to convert the strings back into lists:
import ast
lol2 = map(ast.literal_eval, mylol) # [['1466279297', '703.0'], ...]
Now, you can simply get int and float values from lol2:
newlol = [[int(a[0]), float(a[1])] for a in lol2]
total=0
line=input()
line = line.upper()
names = {}
(tag,text) = parseLine(line) #initialize
while tag !="</PLAY>": #test
if tag =='<SPEAKER>':
if text not in names:
names.update({text})
I seem to get this far and then draw a blank.. This is what I'm trying to figure out. When I run it, I get:
ValueError: dictionary update sequence element #0 has length 8; 2 is required
Make an empty dictionary
Which I did.
(its keys will be the names of speakers and its values will be how many times s/he spoke)
Within the if statement that checks whether a tag is <SPEAKER>
If the speaker is not in the dictionary, add him to the dictionary with a value of 1
I'm pretty sure I did this right.
If he already is in the dictionary, increment his value
I'm not sure.
You are close, the big issue is on this line:
names.update({text})
You are trying to make a dictionary entry from a string using {text}, python is trying to be helpful and convert the iterable inside the curly brackets into a dictionary entry. Except the string is too long, 8 characters instead of two.
To add a new entry do this instead:
names.update({text:1})
This will set the initial value.
Now, it seems like this is homework, but you've put in a bit of effort already, so while I won't answer the question I'll give you some broad pointers.
Next step is checking if a value already exists in the dictionary. Python dictionaries have a get method that will retrieve a value from the dictionary based on the key. For example:
> names = {'romeo',1}
> print names.get('romeo')
1
But will return None if the key doesn't exist:
> names = {'romeo',1}
> print names.get('juliet')
None
But this takes an optional argument, that returns a different default value
> names = {'romeo',2}
> print names.get('juliet',1)
1
Also note that your loop as it stands will never end, as you only set tag once:
(tag,text) = parseLine(line) #initialize
while tag !="</PLAY>": #test
# you need to set tag in here
# and have an escape clause if you run out of file
The rest is left as an exercise for the reader...
I want to write a list of strings to a binary file. Suppose I have a list of strings mylist? Assume the items of the list has a '\t' at the end, except the last one has a '\n' at the end (to help me, recover the data back). Example: ['test\t', 'test1\t', 'test2\t', 'testl\n']
For a numpy ndarray, I found the following script that worked (got it from here numpy to r converter):
binfile = open('myfile.bin','wb')
for i in range(mynpdata.shape[1]):
binfile.write(struct.pack('%id' % mynpdata.shape[0], *mynpdata[:,i]))
binfile.close()
Does binfile.write automatically parses all the data if variable has * in front it (such in the *mynpdata[:,i] example above)? Would this work with a list of integers in the same way (e.g. *myIntList)?
How can I do the same with a list of string?
I tried it on a single string using (which I found somewhere on the net):
oneString = 'test'
oneStringByte = bytes(oneString,'utf-8')
struct.pack('I%ds' % (len(oneString),), len(oneString), oneString)
but I couldn't understand why is the % within 'I%ds' above replaced by (len(oneString),) instead of len(oneString) like the ndarray example AND also why is both len(oneString) and oneString passed?
Can someone help me with writing a list of string (if necessary, assuming it is written to the same binary file where I wrote out the ndarray) ?
There's no need for struct. Simply join the strings and encode them using either a specified or an assumed text encoding in order to turn them into bytes.
''.join(L).encode('utf-8')