Combining data from two dictionaries is something almost every Python developer runs into, merging config settings, combining API responses, or building a final dataset from multiple sources. Python gives you several clean ways to do this, and picking the right one makes your code easier to read and less likely to cause bugs.<\/p>\n\n\n\n
Merge dictionaries in Python using |, update(), or {**d1, **d2}. Master Python dicts and core concepts with HCL GUVI\u2019s <\/em>Python Zero to Hero course.<\/em><\/strong> <\/em>Start your Python journey here<\/em><\/a><\/p>\n\n\n\n The simplest and most modern way is the merge operator |, available in Python 3.9 and later: merged = dict1 | dict2<\/strong>. For older Python versions, use dictionary unpacking with {**dict1, **dict2}<\/strong> or the update()<\/strong> <\/strong>method. All three produce the same result: a single dictionary combining both.<\/p>\n\n\n\n Python <\/a>3.9 introduced the | operator specifically for dictionaries. It reads naturally and creates a brand new dictionary without touching the originals.<\/p>\n\n\n\n Both dict1 and dict2 stay exactly as they were. This is the recommended approach if you’re on Python 3.9 or newer.<\/p>\n\n\n\n When the same key appears in both dictionaries, the right-hand dictionary always wins.<\/p>\n\n\n\n Here, b exists in both, and dict2’s value (3) overwrites dict1’s value (2). This rule applies to every merge method in this guide; the dictionary on the right always takes priority for shared keys.<\/p>\n\n\n\n If you want to update a dictionary directly instead of creating a new one, use |=<\/strong>.<\/p>\n\n\n\n This modifies config directly, which is useful when you’re applying overrides to a settings dictionary and don’t need to preserve the original.<\/p>\n\n\n\n If your project needs to support Python versions before 3.9, dictionary unpacking is the go-to alternative. It’s been available since Python 3.5.<\/p>\n\n\n\n The ** unpacks each dictionary’s key-value pairs into a new dictionary literal. The result is identical to using the | operator.<\/p>\n\n\n\n Unpacking handles any number of dictionaries in one line, which the | operator can’t do as cleanly.<\/p>\n\n\n\n Dictionaries listed later override earlier ones for shared keys; the same “right wins” rule applies, just extended across multiple dictionaries instead of two.<\/p>\n\n\n\n You can also mix in individual key-value pairs alongside unpacked dictionaries.<\/p>\n\n\n\n This is handy when you need to merge a dictionary and add a couple of extra fields in the same step.<\/p>\n\n\n\n Before Python 3.9, update() was the standard way to merge dictionaries. It’s still widely used and works on every Python 3 version.<\/p>\n\n\n\n Unlike the | operator or unpacking, update() modifies dict1 directly rather than creating a new dictionary. This is a key difference to remember.<\/p>\n\n\n\n If you need to keep dict1 unchanged, copy it first before calling update().<\/p>\n\n\n\n This pattern is common in real codebases where you don’t want a merge operation to have side effects on the original data<\/a>.<\/p>\n\n\n\n Merge dictionaries in Python using |, update(), or {**d1, **d2}. Master Python dicts and core concepts with HCL GUVI\u2019s <\/em>Python Zero to Hero course.<\/em><\/strong> <\/em>Start your Python journey here<\/em><\/a><\/p>\n\n\n\nHow Do You Merge Two Dictionaries in Python?<\/strong><\/h2>\n\n\n\n
Method 1: The Merge Operator (Python 3.9+)<\/strong><\/h2>\n\n\n\n
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dict1 = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} dict2 = {<\/strong>‘c’<\/strong>: 3, <\/strong>‘d’<\/strong>: 4}<\/strong>
<\/strong>merged = dict1 | dict2 <\/strong>print<\/strong>(merged) <\/strong># {‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: 4}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\n
dict1 = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} dict2 = {<\/strong>‘b’<\/strong>: 3, <\/strong>‘c’<\/strong>: 4}<\/strong>
<\/strong>merged = dict1 | dict2 <\/strong>print<\/strong>(merged) <\/strong># {‘a’: 1, ‘b’: 3, ‘c’: 4}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\n
config = {<\/strong>‘debug’<\/strong>: <\/strong>False<\/strong>, <\/strong>‘timeout’<\/strong>: 30} overrides = {<\/strong>‘debug’<\/strong>: <\/strong>True<\/strong>, <\/strong>‘retries’<\/strong>: 3}<\/strong>
<\/strong>config |= overrides <\/strong>print<\/strong>(config) <\/strong># {‘debug’: True, ‘timeout’: 30, ‘retries’: 3}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n Python 3.9<\/strong> introduced the dictionary merge operator (|<\/code>)<\/strong>, making it easier and more intuitive to combine dictionaries. Before its introduction, developers typically used the update()<\/strong> method or dictionary unpacking (**<\/code>)<\/strong>, which often resulted in more verbose code when merging multiple dictionaries. The merge operator improves code readability while providing a concise and expressive syntax for creating new dictionaries from existing ones.\n\n<\/div>\n\n\n\nMethod 2: Dictionary Unpacking With **<\/strong><\/h2>\n\n\n\n
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dict1 = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} dict2 = {<\/strong>‘c’<\/strong>: 3, <\/strong>‘d’<\/strong>: 4}<\/strong>
<\/strong>merged = {**dict1, **dict2} <\/strong>print<\/strong>(merged) <\/strong># {‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: 4}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\n
defaults = {<\/strong>‘color’<\/strong>: <\/strong>‘blue’<\/strong>, <\/strong>‘size’<\/strong>: <\/strong>‘medium’<\/strong>} user_prefs = {<\/strong>‘color’<\/strong>: <\/strong>‘red’<\/strong>} overrides = {<\/strong>‘size’<\/strong>: <\/strong>‘large’<\/strong>, <\/strong>‘font’<\/strong>: <\/strong>‘Arial’<\/strong>}<\/strong>
<\/strong>final<\/strong> = {**defaults, **user_prefs, **overrides} <\/strong>print<\/strong>(<\/strong>final<\/strong>) <\/strong># {‘color’: ‘red’, ‘size’: ‘large’, ‘font’: ‘Arial’}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\n
base = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} extended = {**base, <\/strong>‘c’<\/strong>: 3, <\/strong>‘d’<\/strong>: 4} <\/strong>print<\/strong>(extended) <\/strong># {‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: 4}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Method 3: The update() Method<\/strong><\/h2>\n\n\n\n
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dict1 = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} dict2 = {<\/strong>‘c’<\/strong>: 3, <\/strong>‘d’<\/strong>: 4}<\/strong>
<\/strong>dict1.update(dict2) <\/strong>print<\/strong>(dict1) <\/strong># {‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: 4}<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n\n
dict1 = {<\/strong>‘a’<\/strong>: 1, <\/strong>‘b’<\/strong>: 2} dict2 = {<\/strong>‘c’<\/strong>: 3, <\/strong>‘d’<\/strong>: 4}<\/strong>
<\/strong>merged = dict1.copy() merged.update(dict2)<\/strong>
<\/strong>print<\/strong>(merged) <\/strong># {‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: 4} print(dict1) # {‘a’: 1, ‘b’: 2} unchanged<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nComparing All Three Methods<\/strong><\/h2>\n\n\n\n