python for loop as elif statement in function

Question

I am trying to insert a for loop inside a function that loops through values from a list.

Consider I have the following dataframe:

import pandas as pd

df = pd.DataFrame()

df['A'] = (53.104898,   52.032832,  48.705107,  43.150132,  42.09353,   42.32076,   41.620527,  44.479339,  44.673272,  43.811447,  44.273042,  47.384234,  49.210512,  50.330492   ,48.808856, 49.543268,  43.460175,  41.54373,   49.618678,  44.988629,  52.964725,
56.358917,  53.366254)
df['B'] = (2.157,2.0826,0.8452,-0.3046,-0.3436,-0.3906,-1.1528,-0.9462,-1.1314,-0.9994,-1.0538,0.785,1.5334,0.1424, 0.764,-0.6844,-2.5798,-2.3644,-1.97,-3.7466,-1.862,-0.248, -0.456)

def func():
    q = [40,60]

    def valuation_formula(x, y):

        for i in q:
            if x > 3.9:
                return 'SIT'
            elif x < -3.8:
                return 'SIT'
            elif x > 0.00 and y > i:
                return 'BUY'
            elif x < 0.00 and y < 41.14:
                return 'SELL'
            else:
                return 'SIT'

    df['C'] = df.apply(lambda row: valuation_formula(row['A'], row['B']), axis=1)

    print(df)
    i=i+1

func()

Actual results should be 2 seperate dataframes. 1 dataframe using 40 as i from list q and second using 60

Your loop never looks past the first value in q, because you return from the function in every possible path. — chepner
– chepner, Commented Aug 2, 2019 at 12:50
You seem to be incrementing i, which doesn't need to be done as it's inside a for loop. Also, where you increment it, it is not defined. — clubby789
– clubby789, Commented Aug 2, 2019 at 12:54

Derlin · Accepted Answer · 2019-08-02 12:55:20Z

2

As mentioned in the comments, a return inside a loop will terminate everything, so you will only look at the first value of q. Also, you are mixing for i in q and i+=1...

Anyway, a quick fix is:

q = [40,60]

def valuation_formula(i, x, y):
    # pass the i as a parameter
    if x > 3.9:
        return 'SIT'
    elif x < -3.8:
        return 'SIT'
    elif x > 0.00 and y > i:
        return 'BUY'
    elif x < 0.00 and y < 41.14:
        return 'SELL'
    else:
        return 'SIT'

# loop here
for i in q:
    df['C'] = df.apply(lambda row: valuation_formula(i, row['A'], row['B']), axis=1)
    print(df)

answered Aug 2, 2019 at 12:55

Derlin

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1 Comment

ds882 Over a year ago

thank you this is the correct answer I was looking for

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