I'm getting Key error in python

In my python program I am getting this error:

KeyError: 'variablename' 

From this code:

path = meta_entry['path'].strip('/'), 

Can anyone please explain why this is happening?

8 Answers

A KeyError generally means the key doesn't exist. So, are you sure the path key exists?

From the official python docs:

exception KeyError

Raised when a mapping (dictionary) key is not found in the set of existing keys.

For example:

>>> mydict = {'a':'1','b':'2'} >>> mydict['a'] '1' >>> mydict['c'] Traceback (most recent call last): File "<stdin>", line 1, in <module> KeyError: 'c' >>> 

So, try to print the content of meta_entry and check whether path exists or not.

>>> mydict = {'a':'1','b':'2'} >>> print mydict {'a': '1', 'b': '2'} 

Or, you can do:

>>> 'a' in mydict True >>> 'c' in mydict False 

I fully agree with the Key error comments. You could also use the dictionary's get() method as well to avoid the exceptions. This could also be used to give a default path rather than None as shown below.

>>> d = {"a":1, "b":2} >>> x = d.get("A",None) >>> print x None 

For dict, just use

if key in dict

and don't use searching in key list

if key in dict.keys()

The latter will be more time-consuming.

Yes, it is most likely caused by non-exsistent key.

In my program, I used setdefault to mute this error, for efficiency concern. depending on how efficient is this line

>>>'a' in mydict.keys() 

I am new to Python too. In fact I have just learned it today. So forgive me on the ignorance of efficiency.

In Python 3, you can also use this function,

get(key[, default]) [function doc][1] 

It is said that it will never raise a key error.

I received this error when I was parsing dict with nested for:

cats = {'Tom': {'color': 'white', 'weight': 8}, 'Klakier': {'color': 'black', 'weight': 10}} cat_attr = {} for cat in cats: for attr in cat: print(cats[cat][attr]) 

Traceback:

Traceback (most recent call last): File "<input>", line 3, in <module> KeyError: 'K' 

Because in second loop should be cats[cat] instead just cat (what is just a key)

So:

cats = {'Tom': {'color': 'white', 'weight': 8}, 'Klakier': {'color': 'black', 'weight': 10}} cat_attr = {} for cat in cats: for attr in cats[cat]: print(cats[cat][attr]) 

Gives

black 10 white 8 

Let us make it simple if you're using Python 3

mydict = {'a':'apple','b':'boy','c':'cat'} check = 'c' in mydict if check: print('c key is present') 

If you need else condition

mydict = {'a':'apple','b':'boy','c':'cat'} if 'c' in mydict: print('key present') else: print('key not found') 

For the dynamic key value, you can also handle through try-exception block

mydict = {'a':'apple','b':'boy','c':'cat'} try: print(mydict['c']) except KeyError: print('key value not found')mydict = {'a':'apple','b':'boy','c':'cat'} 

This means your array is missing the key you're looking for. I handle this with a function which either returns the value if it exists or it returns a default value instead.

def keyCheck(key, arr, default): if key in arr.keys(): return arr[key] else: return default myarray = {'key1':1, 'key2':2} print keyCheck('key1', myarray, '#default') print keyCheck('key2', myarray, '#default') print keyCheck('key3', myarray, '#default') 

Output:

1 2 #default 

For example, if this is a number :

ouloulou={ 1:US, 2:BR, 3:FR } ouloulou[1]() 

It's work perfectly, but if you use for example :

ouloulou[input("select 1 2 or 3"]() 

it's doesn't work, because your input return string '1'. So you need to use int()

ouloulou[int(input("select 1 2 or 3"))]()