A string = 1 2 3 4
Program should return = [[1,2],[3,4]]
in python
I want the string to be converted into a list of every two element from string
You could go for something very simple such as:
s = "10 2 3 4 5 6 7 8"
l = []
i = 0
list_split_str = s.split() # splitting the string according to spaces
while i < len(s) - 1:
l.append([s[i], s[i + 1]])
i += 2
This should output:
[['10', '2'], ['3', '4'], ['5', '6'], ['7', '8']]
You could also do something a little more complex like this in a two-liner:
list_split = s.split() # stripping spaces from the string
l = [[a, b] for a, b in zip(list_split[0::2], list_split[1::2])]
The slice here means that the first list starts at index zero and has a step of two and so is equal to [10, 3, 5, ...]. The second means it starts at index 1 and has a step of two and so is equal to [2, 4, 6, ...]. So we iterate over the first list for the values of a and the second for those of b.
zip returns a list of tuples of the elements of each list. In this case, [('10', '2'), ('3', '4'), ('5', '6'), ...]. It allows us to group the elements of the lists two by two and iterate over them as such.
This also works on lists with odd lengths.
For example, with s = "10 2 3 4 5 6 7 ", the above code would output:
[['10', '2'], ['3', '4'], ['5', '6']]
disregarding the 7 since it doesn't have a buddy.
here is the solution if the numbers exact length is divisible by 2
def every_two_number(number_string):
num = number_string.split(' ')
templist = []
if len(num) % 2 == 0:
for i in range(0,len(num),2):
templist.append([int(num[i]),int(num[i+1])])
return templist
print(every_two_number('1 2 3 4'))
you can remove the if condition and enclosed the code in try and except if you want your string to still be convert even if the number of your list is not divisible by 2
def every_two_number(number_string):
num = number_string.split(' ')
templist = []
try:
for i in range(0,len(num),2):
templist.append([int(num[i]),int(num[i+1])])
except:
pass
return templist
print(every_two_number('1 2 3 4 5'))
I am trying to contact the CSV rows. I tried to convert the CSV rows to list by pandas but it gets 'nan' values appended as some files are empty.
Also, I tried using zip but it concats column values.
with open(i) as f:
lines = f.readlines()
res = ""
for i, j in zip(lines[0].strip().split(','), lines[1].strip().split(',')):
res += "{} {},".format(i, j)
print(res.rstrip(','))
for line in lines[2:]:
print(line)
I have data as below,
Input data:-
Input CSV Data
Expected Output:-
Output CSV Data
The number of rows are more than 3,only sample is given here.
Suggest a way which will achieve the above task without creating a new file. Please point to any specific function or sample code.
This assumes your first line contains the correct amount of columns. It will read the whole file, ignore empty data ( ",,,,,," ) and accumulate enough data points to fill one row, then switch to the next row:
Write test file:
with open ("f.txt","w")as f:
f.write("""Circle,Year,1,2,3,4,5,6,7,8,9,10,11,12
abc,2018,,,,,,,,,,,,
2.2,8.0,6.5,9,88,,,,,,,,,,
55,66,77,88,,,,,,,,,,
5,3.2,7
def,2017,,,,,,,,,,,,
2.2,8.0,6.5,9,88,,,,,,,,,,
55,66,77,88,,,,,,,,,,
5,3.2,7
""")
Process test file:
data = [] # all data
temp = [] # data storage until enough found , then put into data
with open("f.txt","r") as r:
# get header and its lenght
title = r.readline().rstrip().split(",")
lenTitel = len(title)
data.append(title)
# process all remaining lines of the file
for l in r:
t = l.rstrip().split(",") # read one lines data
temp.extend( (x for x in t if x) ) # this eliminates all empty ,, pieces even in between
# if enough data accumulated, put as sublist into data, keep rest
if len (temp) > lenTitel:
data.append( temp[:lenTitel] )
temp = temp [lenTitel:]
if temp:
data.append(temp)
print(data)
Output:
[['Circle', 'Year', '1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12'],
['abc', '2018', '2.2', '8.0', '6.5', '9', '88', '55', '66', '77', '88', '5', '3.2', '7'],
['def', '2017', '2.2', '8.0', '6.5', '9', '88', '55', '66', '77', '88', '5', '3.2', '7']]
Remarks:
your file cant have leading newlines, else the size of the title is incorrect.
newlines in between do not harm
you cannot have "empty" cells - they get eliminated
As long as nothing weird is going on in the files, something like this should work:
with open(i) as f:
result = []
for line in f:
result += line.strip().split(',')
print(result)
Today I was trying to open a file and build some list from the data of the file. I am using the with statement. But I have the following doubt:
If I write the following code:
def Preset_wheel_filler(self):
"""
Complete the Preset_wheel and also apply preset values when one
preset is selected.
"""
with open('Preset.txt', 'r') as PresetFile:
Presets = [line.split()[1:] for line in PresetFile if 'name:'
in line.split()]
with open('Preset.txt', 'r') as PresetFile:
channel_list = ['1', '2', '3', '4', '5', '6', '7', '8']
Preset_values = [line.split() for line in PresetFile for
y in channel_list if y in line.split()]
print(len(Preset_values))
The length of the last list created is 16. (Which is correct)
Now, if I rearrange the code like this:
def Preset_wheel_filler(self):
"""
Complete the Preset_wheel and also apply preset values when one
preset is selected.
"""
with open('Preset.txt', 'r') as PresetFile:
Presets = [line.split()[1:] for line in PresetFile if 'name:'
in line.split()]
channel_list = ['1', '2', '3', '4', '5', '6', '7', '8']
Preset_values = [line.split() for line in PresetFile for
y in channel_list if y in line.split()]
print(len(Preset_values))
The printed length is 0.
My question is: Why should I write the with open statement twice?
Thanks in advance.
Files are stream based. Once you read all the data in the file its position pointer is at the end and nothing can be read anymore. You "could" seek to 0 to fix that, but - you have the full line in the first go, simply parse both things from it.
PresetFile.seek(0) # goes back to the beginning of the file.
See https://docs.python.org/3/tutorial/inputoutput.html#methods-of-file-objects
for details on how to use seek and maybee peek into https://docs.python.org/3/library/functions.html#open
again.
SEE UPDATE BELOW!
For my Python program I need to write 3 different lists to a csv file, each in a different column. Each lists has a different size.
l1 = ['1', '2', '3', '4', '5']
l2 = ['11', '22', '33', '44']
l3 = ['111', '222', '333']
f = 'test.csv'
outputFile = open(f, 'w', newline='')
outputWriter = csv.writer(resultFile, delimiter=';')
outputWriter.writerow(headerNames)
for r in l3:
resultFile.write(';' + ';' + r + '\n')
for r in l2:
resultFile.write(';' + r + '\n')
for r in l1:
resultFile.write(r + '\n')
resultFile.close()
Unfortunately this doesn't work. The values of the lists are written below each other list in the column to the right. I would prefer to have the list values written beside one another just like this:
1;11;111
2;22;222
etc.
I am sure there is an easy way to get this done, but after hours of trying I still cannot figure it out.
UPDATE:
I tried the following. It is progress, but I am still not there yet.
f = input('filename: ')
l1 = ['1', '2', '3', '4', '5']
l2 = ['11', '22', '33', '44']
l3 = ['111', '222', '333']
headerNames = ['Name1', 'Name2', 'Name3']
rows = zip(l1, l2, l3)
with open(f, 'w', newline='') as resultFile:
resultWriter = csv.writer(resultFile, delimiter=';')
resultWriter.writerow(headerNames)
for row in rows:
resultWriter.writerow(row)
It write the data in the format I would like, however the values 4, 5 and 44 are not writen.
Your first attempt is not using the csv module properly, nor transposing the rows like your second attempt does.
Now zipping the rows will stop as soon as the shortest row ends. You want itertools.ziplongest instead (with a fill value of 0 for instance)
import itertools,csv
f = "out.csv"
l1 = ['1', '2', '3', '4', '5']
l2 = ['11', '22', '33', '44']
l3 = ['111', '222', '333']
headerNames = ['Name1', 'Name2', 'Name3']
rows = itertools.zip_longest(l1, l2, l3, fillvalue=0)
with open(f, 'w', newline='') as resultFile:
resultWriter = csv.writer(resultFile, delimiter=';')
resultWriter.writerow(headerNames)
resultWriter.writerows(rows) # write all rows in a row :)
output file contains:
Name1;Name2;Name3
1;11;111
2;22;222
3;33;333
4;44;0
5;0;0
I am facing a problem to convert from List to tuple. For example i have lists like this
['1', '9']
['2']
['3']
['4']
I want output like this
[(1,9),(2),(3),(4)]
Kindly help me. I am not getting any way.
If you have a list 'l' then you can call the builtin function 'tuple' on it to convert to a tuple
l = [1,2]
tup = tuple(l)
print tup # (1,2)
if you have a list of list l = [['1', '9'], ['2'], ['3'], ['4']]
you can do :
l = [['1', '9'], ['2'], ['3'], ['4']]
tups = map(lambda x: tuple(x), l)
print tups # [(1,9),(2),(3),(4)]