Append a dictionary to a dictionary

Append method breakdown

Modifying original vs preserving dictionary

Are you a conservationist at heart? To keep the original dictionaries safe and unscathed, copy the original before update:

orig = {'a': 1}
extra = {'b': 2}
# Let's clone orig and also give it a cool new name, dest
dest = dict(orig)
dest.update(extra)
# Now dest = {'a': 1, 'b': 2} and orig remains untouched, like a rare piece of art!


Using Union Operator in Python 3.9+

Python 3.9 has outdone itself by introducing the | (union) operator for dictionaries:

orig = {'a': 1}
extra = {'b': 2}
dest = orig | extra
# Who knew a simple '|' could hold so much power? Thanks Python 3.9!


Dealing with large datasets efficiently

Fret not! The update() method is very efficient with large dictionaries and saves you from writing excess loops:

# Let's handle some big data. Imagine big_dict1 and big_dict2 are encyclopedia-sized dictionaries
big_dict1.update(big_dict2)
# Just one line of code to handle all that data? Yes please!


Handling key conflicts during merge

In the game of keys, the newcomer wins! When keys conflict during merge, the new values overwrite the old ones.

dict1 = {'x': 1, 'y': 2}
dict2 = {'y': 3, 'z': 4}
dict1.update(dict2)
# In dict1, 'y' bows down to the new 'y' from dict2. All hail the new 'y'!


Advanced dictionary operations

Merge multiple dictionaries using itertools

To merge multiple dictionaries:

import itertools

dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
dict3 = {'c': 5, 'd': 6}

combined_dict = dict(itertools.chain.from_iterable(d.items() for d in [dict1, dict2, dict3]))
# Looks like we've created a monster...dictionary!


Dictionary comprehensions and custom logic

Dictionary comprehensions help to introduce custom logic during merge:

dict1 = {'a': 1}
dict2 = {'b': 2, 'a': 3}

merged_dict = {k: dict2[k] if k in dict2 else dict1[k] for k in dict1.keys() | dict2.keys()}
# Congratulations! You've just married dictionary comprehensions and custom logic!


Python 2.x merge method

For those who time traveled from the year 2000, Python 2.x merge method is:

merged_dict = dict(dict1.items() + dict2.items())
# Yes, old-school is cool too!
