KeyError looping through multiple values per key

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Iterating over dictionaries using 'for' loops 12 answers

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T is the key, so you should iterate with for T in instruments :

import math

instruments = {} 

def add_instrument(par, T, coup, price, compounding_freq = 2):
  instruments[T] = (par, coup, price, compounding_freq)

add_instrument(100, 0.25, 0., 97.5)
add_instrument(100, 0.5, 0., 94.9)
add_instrument(100, 1.0, 3., 90.)
add_instrument(100, 1.5, 8, 96., 2)

for T in instruments:
    par, coupon, price, freq = instruments[T]
    if coupon == 0:
        print(T)

If you use for T in instruments.items() , T becomes a tuple of (key, value) . When you then look for instruments[T] , there's no such key in the dict.

You could also unpack the value tuple directly if you insist on using items() :

for t, (par, coup, price, freq) in instruments.items():
    if coup == 0:
        print(t)

It outputs:

0.25
0.5

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