Concatenate two lists in Python
David Y.
The Problem
How can I concatenate two lists in Python? In other words, how can I join two or more lists together to make one big list?
The Solution
We can do this using Python’s built-in operator overloading. When used with lists, the + operator will concatenate them, as shown below:
list1 = ["Apples", "Oranges", "Bananas"] list2 = ["Pears", "Grapes", "Pineapples"] combined = list1 + list2 print(combined) # output: ['Apples', 'Oranges', 'Bananas', 'Pears', 'Grapes', 'Pineapples']
Alternatively, we can use list.extend(), which will modify the first list:
list1 = ["Apples", "Oranges", "Bananas"] list2 = ["Pears", "Grapes", "Pineapples"] list1.extend(list2) print(list1) # output: ['Apples', 'Oranges', 'Bananas', 'Pears', 'Grapes', 'Pineapples']
To concatenate three or more lists, we can also use the + operator:
list1 = ["Apples", "Oranges", "Bananas"] list2 = ["Pears", "Grapes", "Pineapples"] list3 = ["Tangerines", "Apricots"] list4 = ["Pomegranates", "Watermelons", "Raspberries"] combined = list1 + list2 + list3 + list4 print(combined) # output: ['Apples', 'Oranges', 'Bananas', 'Pears', 'Grapes', 'Pineapples', 'Tangerines', 'Apricots', 'Pomegranates', 'Watermelons', 'Raspberries']
However, when combining more than two lists, itertools.chain() is more performant. Note that this method outputs an itertools.chain object, which must be typecast to a list, as shown below:
from itertools import chain list1 = ["Apples", "Oranges", "Bananas"] list2 = ["Pears", "Grapes", "Pineapples"] list3 = ["Tangerines", "Apricots"] list4 = ["Pomegranates", "Watermelons", "Raspberries"] combined = list(chain(list1, list2, list3, list4)) print(combined) # output: ['Apples', 'Oranges', 'Bananas', 'Pears', 'Grapes', 'Pineapples', 'Tangerines', 'Apricots', 'Pomegranates', 'Watermelons', 'Raspberries']
Ask a questionImprove this Answer
Related Answers
- Access the index of a for loop
- Accessing the Index in a `for` Loop in Python
- Append vs. extend in Python
- Change the size of figures drawn with Matplotlib in Python
- Check if a dictionary contains a key in Python
- Check if a list is empty in Python
- Convert a list to a string 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
- Delete a file or folder 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
- How to manage feature flags without making performance worse
- Find the current directory and executed file's directory in Python
- Get the length of a list in Python
- How do I parse a string to a float or int?
- What does `if __name__ == "__main__":` do?
- Iterate over rows in a Pandas DataFrame in Python
- Limit floats to two decimal points in Python
- Is There a List of pytz Timezones?
- Lowercase a string in Python
- Making a list out of a list of lists in Python?
- Pandas DataFrame row count in Python
- Add new keys to a dictionary in Python
- Sort a dictionary by value in Python
- Iterate over a dictionary in Python
- List files in a directory using Python
- How Do I Merge Two Dictionaries in a Single Expression (Take Union of Dictionaries)?
- How Can I Safely Create a Nested Directory?
- Python slice notation
- Does Python Have a Ternary Conditional Operator?
- 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
- Rename columns in a Python Pandas DataFrame
- Running External Programs in Python
- Select multiple columns in Python Pandas
- Select rows from a Python Pandas DataFrame based on column values
- TypeError 'str' Object Does Not Support Item Assignment
- 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?