Reading in files and returning strings in python

A simple approach is to read all lines of a file into a list, then find the index in that list based on the year you want, and get the next line.

with open('students.txt', 'r') as f:
    data = [i.strip() for i in f]   # strip trailing space

year = input("Enter year: ")
try:
    # find index, get the next line
    line = data[data.index(year) + 1] 
    # split on whitespace, apply float()
    item_list = [float(i) for i in line.split()]
except ValueError:  # raised if year not found
    print("No relevant data")

Print next not empty line after line that is equal required year.

year = "2013"

with open("students.txt") as f:
    stop = False
    for line in f:
        line = line.rstrip("\n")
        if line == year:
            stop = True
        else:
            if line and stop:
                print line.split()
                break

    if not stop:
        print "No data for year {}.".format(year)

Instead try reading all the entries into a dictionary. Then its simple to query by year.

def readentries(f):    
    # read until we get `StopException` i.e. end of file
    while True:
        try:
            # take two lines from the file and strip newlines
            # and split heights by spaces to give a list of heights
            yield next(f).strip(), next(f).strip().split()
        except StopIteration:
            # break out of the infinite while loop
            break

with open('heights.txt') as f:
     entries = dict(readentries(f))

year = input("Enter the year for the data you want to receive: ")

# query dict for supplied entry
if year in entries:
    print('for year %s we have heights %s ' % (year, ', '.join(entries[year])))
else:
    print('no data')

You may want to convert the heights to float variables. This would be easy to add.

When you do f.readline().split(), you get a list. So for the first line, you would have something like line == ['2013']. On the other hand, year is a string. So if the user put in 2013, type(year) == <class 'str'> while type(line) == <class 'list'>. Because they are never equal to each other, the if clause is never True and the line never gets printed.

#read in text file
f = open("students.txt")
#ask for student year
year = input("Enter the year for the data you want to receive:")
#check to see if year is available
for line in f.readlines():
    if year in line:
        f.readline()
        print ( f.readline() )
        break

Above code wouldn't work if there's a student whose height is over 2,000, I suppose.

You can also build two lists and construct a dictionary by iterating over the lines of thhe file:

with open("grade.txt", "r") as file:
    year = []
    height = []
    for i in file:
        if len(i.strip("\n")) == 4:
            year.append(i.strip("\n"))
        elif i != "\n":
            height.append(i.strip("\n").split(" "))
    ydict = {year[i]: height[i] for i in range(len(year))}

print(ydict['2013'])

Since the data includes some blanks lines and tabs, you'll want to clean it up first. Then it's just a matter of added the even numbered rows (years) as keys (starting at zero) in a dictionary and the odd numbered rows (heights) as values in the dictionary.

year = input("Enter the year for the data you want to receive:")
with open("students.txt") as f:
    # read stripped file lines into list keeping only those that contain data
    data = [line.strip() for line in f.readlines() if line.strip() != '']
# build a dict from the data using list slicing to get the years (keys) and heights (values)
data_dict = dict(zip(data[0::2], data[1::2]))
# print the heights if the year exists otherwise 'No data.'
print(data_dict.get(str(year)) if data_dict.get(str(year)) else 'No data.')