Add new keys to a dictionary in Python
David Y.
The Problem
How can I add new keys to a dictionary in Python?
The Solution
Python provides a few different ways to add new key-value pairs to an existing dictionary. The simplest way is to assign a value to a new key using Python’s indexing/square brackets syntax:
prices = {"Apple": 1, "Orange": 2} # existing dictionary prices["Avocado"] = 3 # new key-value pair print(prices) # will print {"Apple": 1, "Orange": 2, "Avocado": 3}
This same syntax can be used to update existing key-value pairs:
prices["Apple"] = 2 print(prices) # will print {"Apple": 2, "Orange": 2, "Avocado": 3}
To add and update multiple key-value pairs at once, we can use Python’s dict.update() method:
prices.update({"Pear": 2, "Grapefruit": 2, "Orange": 3}) # adds Pear and Grapefruit, and updates Orange print(prices) # will print {"Apple": 2, "Orange": 3, "Avocado": 3, "Pear": 2, "Grapefruit": 2}
You can also use the dictionary comprehension and dictionary constructor together to add or update the key-value pairs:
prices = {**prices, **{"Pear": 2, "Grapefruit": 2, "Orange": 3}} print(prices) # will print {"Apple": 2, "Orange": 3, "Avocado": 3, "Pear": 2, "Grapefruit": 2}
As of Python 3.9, we can use the update operator (|=) instead of the update() method:
prices |= {"Pear": 2, "Grapefruit": 2, "Orange": 3} # adds Pear and Grapefruit and updates Orange print(prices) # will print {"Apple": 2, "Orange": 3, "Avocado": 3, "Pear": 2, "Grapefruit": 2}
Ask a questionImprove this Answer
Related Answers
- Check if a string is empty in Python
- Access environment variables in Python
- Access the index of a for loop
- Accessing the Index in a `for` Loop in Python
- Append vs. extend in Python
- Add a new column to a DataFrame in Python Pandas
- Change the size of figures drawn with Matplotlib in Python
- Check for NaN values in Python
- Check if a dictionary contains a key in Python
- Check if a list is empty in Python
- Concatenate two lists in Python
- How Can I Safely Create a Nested Directory?
- Python slice notation
- Does Python Have a Ternary Conditional Operator?
- Raise an exception in Python
- How Do I Merge Two Dictionaries in a Single Expression (Take Union of Dictionaries)?
- What Does the `yield` Keyword in Python Do?
- Read a file line by line into a list Python
- Remove element from a list by index in Python
- Remove whitespace from a string in Python
- Rename columns in a Python Pandas DataFrame
- Convert a list to a string in Python
- Convert a string to bytes in Python
- Convert an integer to a string in Python
- Convert bytes to a string in Python
- Convert a string containing a date into datetime in Python
- Copy files in Python
- Count occurrences of item in Python list
- Declare an array in Python
- Define a two-dimensional array in Python
- Delete a column from a DataFrame in Python Pandas
- Delete a file or folder in Python
- Delete element from a dictionary in Python
- Determine the type of a Python variable
- Difference between `@staticmethod` and `@classmethod` function decorators in Python
- Extract a substring from a string in Python
- Fastest way to check if a list contains an item in Python
- How to manage feature flags without making performance worse
- Find all files in a directory with a given extension using Python
- Find item in list in Python
- Find the current directory and executed file's directory in Python
- Generate random integers within a range in Python
- Get key by value in dictionary Python
- Get the current script file's full directory path in Python
- Get the current time in Python
- Get the last element of a list in Python
- Get the length of a list in Python
- Get unique values from a list in Python
- How do I append one string to another in Python?
- How do I parse a string to a float or int?
- How do I remove a trailing newline from a string in Python
- What does `if __name__ == "__main__":` do?
- Import files from a different folder in Python
- Indentation errors in Python
- Install a specific version of a Python package using PIP
- Install Python packages from a local package index
- Invalid literal for int error in Python
- Iterate over rows in a Pandas DataFrame in Python
- Limit floats to two decimal points in Python
- Is There a List of pytz Timezones?
- Logical AND (&&) in Python
- Lowercase a string in Python
- Making a list out of a list of lists in Python?
- Measure elapsed time in Python
- Pandas DataFrame row count in Python
- Print multiple times without newlines or spaces in Python
- Sort a dictionary by value in Python
- Python equivalent of a ternary operator: if-then-else in one line
- Iterate over a dictionary in Python
- List files in a directory using Python
- Running External Programs in Python
- Save a Matplotlib plot to a file in Python
- Select multiple columns in Python Pandas
- Select rows from a Python Pandas DataFrame based on column values
- Slicing in Python
- Split statements across multiple lines in Python code
- TypeError 'str' Object Does Not Support Item Assignment
- `super()` and `__init__()` in Python
- Switch-case statement equivalents in Python
- Time delay in Python
- UnboundLocalError Local Variable 'index' Referenced Before Assignment
- Upgrade specific `pip` packages in Python
- Use global variables in Python functions
- What are Python Metaclasses?
- Write one or more lines to a file in Python