CODEWITHSUNDEEP
python
Bijan
Bijan

Reputation: 8586

Python Find Min Value In Array

Im trying to find the max/min values of the first column in an array short of importing anything

max = 0
min = 100000

for row in _file_in.readlines():
    Data = row.split(',') # Load first column
    if (Data[0] > max):
        max = Data[0]
    if (Data[0] < min):
        min = Data[0]
print min, max

I initialize max to 0 and min to some arbitrarily large number. My resulting code is able to print out the max # but the minimum # is printing out 100000 which is incorrect

Upvotes: 0

Views: 2779

Answers (2)

AChampion
AChampion

Reputation: 30258

An alternative, you could create a generator for your first_col and then just iterate over it. No need for any artificial initialisation of mn or mx. Is memory efficient and only iterates over the column once:

first_col = (int(row.split(',')[0]) for row in _file_in)
mn = mx = next(first_col, None)
for i in first_col:
    if i < mn:
        mn = i
    elif i > mx:
        mx = i
print mn, mx

For an empty file it will print (None, None)

Upvotes: 2

mgilson
mgilson

Reputation: 309831

It looks like your data is from a file and so you're comparing a string to a number. In python2.x, the result from the comparison is only guaranteed to be consistent (the spec doesn't tell us what the result actually is).

You'll want to convert your strings to some sort of numeric type... e.g. first_col = float(Data[0]) for the comparison.

for row in _file_in.readlines():
    Data = row.split(',') # Load first column
    first_col = float(Data[0])
    if (first_col > max):
        max = Data[0]
    if (first_col < min):
        min = Data[0]
    print min, max

Note, we can do a whole lot better using builtin functions and list-comprehensions:

first_col = [float(row.split(',')[0]) for row in _file_in]
print min(fist_col), max(first_col)

Notice that we didn't have to specify any artificial minima or maxima compared to your original solution, so this would work with input that consisted of entirely negative numbers (for example).

Upvotes: 3

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