This question is totally simple, but i don't get it done since hours: I got a datafile, that contains two columns of data, separated by an tab. I want to read and process them with python. allData contains the data, but how can i access parts of it?
with open( "file.txt", "r" ) as mergeData:
allData = mergeData.read()
print allData
The most flexible way would be to use the csv module:
import csv
with open("file.txt", "rb") as infile:
reader = csv.reader(infile, delimiter="\t")
allData = list(reader)
Note that all the elements will be strings. If you want to convert, say, the first column to an int and the second column to a float, you could do something like
allData = [(int(first), float(second)) for first,second in reader]
To split it up into two lists of floats, one for each column, use zip() together with the tuple unpacking operator (*):
first, second = zip(*((float(x), float(y)) for x,y in reader))
allData is a list, not a file. At which point do you want to split that?Short and simple:
with open( "file.txt", "r" ) as mergeData:
allData = [line.strip().split('\t') for line in mergeData]
csv module mentioned by @TimPietzcker is nice but doesn’t handle unicode.
csv module handles Unicode.Thecsv module is a good choice for reading in files of delimited data fields. The following creates a list of lists, and each one will contain the data read from the corresponding column in the data file. It can also easily be adapted to any number of columns of data:
import csv
NUM_COLS = 2
columns = [[] for _ in range(NUM_COLS)]
with open("datafile.txt", "rb") as infile:
for row in csv.reader(infile, delimiter="\t"):
for i, col in enumerate(row):
columns[i].append(col)
for col in columns:
print col
Sample tab-delimited input file:
1 5
2 6
3 7
4 8
Output produced:
['1', '2', '3', '4']
['5', '6', '7', '8']
why not:
fp = open("file.txt","r")
mylist = fp.readlines() # get list of lines.
fp.close() # i forgot that line [EDIT]
for i in range(len(mylist)):
mylist[i] = mylist[i].strip() #get rid of ' ' and '\n' and such
mylist[i] = mylist[i].split('separator') # splits line into list of elements in the line
mylist should then be a 2D array / list of your lines and single elements in each line. separator should then be swapped with the char or string that separates your line elements.
.strip() line...) and is quite unpythonic and inefficient.
mylist 2. Lists are iterable too so you don't need indexes 3. If you really need indexes most of the time enumarate is cleaner if not more effective.;s). Strings are immutable. Building a list of strings first, then chopping that into a list of a list of strings is very slow and memory-inefficient. Plus the problems outlined by @zero323.split('separator').