Counting which numbers fall in a certain bracket
Notes:


Creating so many variables is a warning sign that they should be grouped  somehow (an object, a dictionary, ...). I'd use a dictionary here.
Consider learning some functional programming (as opposed to imperative programming) to apply it when it improves the code (IMO: most of the time). Here it means basically using collections.counter and generator expressions.
Don't read whole files, read them line by line: for line in file_descriptor.
There are programmatic ways of detecting intervals of numbers (simple loop, binary search). However, since you have here only 5 intervals it's probably fine just to write a conditional as you did. If you had, let's say 20 intervals, a conditional branch would be a very sad thing to see.
Conditional branches are more clear when you use non-overlapping conditions with if/elif/else (effectively working as expressions instead of statements).


I'd write:

from collections import Counter

def get_interval(x):
    if x &gt; 70:
        return "greater70"
    elif 60 &lt;= x &lt; 70:
        return "sixtys"    
    elif x &gt;= 50:
        return "fiftys"
    elif x &gt;= 40:
        return "fortys" 
    elif x == -1:
        return "nomarks"   

with open("inputfile.txt") as file:
    counter = Counter(get_interval(int(n)) for line in file for n in line.split(","))
# Counter({'sixtys': 10, 'greater70': 10, None: 7, ..., 'fortys': 4})