Q:

Converting floating point number to any base

How would i convert a float, represented by a string, to a decimal, base between 2 to 36 in Python, without using Python built ins int and float?
meaning: 
convert_float("234.56", base) --> float, or ("10AB", base) --> float
In case that the float ends in .0, the result should be an integer.
Converting integers to any base seems much less complicated, however I couldn't come up or find any solution for the floats.

A:

I think your idea was quite good already. To implement it, you would first need a dictionary that can convert strings to integers. Then you'd want to split your string into two, at the decimal point. Then, you could reverse your "before" string and iterate through it, multiplying the integer of the current value with 10 to the current index and adding all these values up.
Then, iterate through your "after" string and multiply the current value with the negative current index, adding the values again.
To put this into code:
s2i = {"0": 0,
"1": 1,
"2": 2,
...
"Y": 34,
"Z": 35
}

def convert_float(s, base=10):
    ret = 0
    if "." not in s: bef = s
    else: bef, aft = s.split(".")
    for i in enumerate(reversed(bef)):
        integer = s2i[i[1]]
        if integer >= base: raise ValueError
        ret += base**i[0] * integer
    if "." not in s: return ret
    for i in enumerate(aft):
        integer = s2i[i[1]]
        if integer >= base: raise ValueError
        ret += base**-(i[0] + 1) * integer
    return ret

print convert_float("YF.1G90N", 36)

> 1239.04031674

