Or, as the Python interpreter reports: Traceback (most recent call last):Ĭsv_mapping_list.sort(key=lambda item: item.get("Age"))Ĭsv_mapping_list = sorted(csv_mapping_list, key=lambda item: item.get("Age"))Īs usual, I appreciate your support. Here, we have to specify the key parameter as dictionaries cannot be naturally sorted. csv_mapping_list.sort(key=lambda item: item.get("Age")) In the following snippet, we sort the list of dictionaries by age. Instead, we can use the builtin sort function for lists. Luckily for us, we don’t have to implement sorting by hand in Python. to sort the list of dictionaries by key age, name (like in SQL statement ORDER BY age, name), you can use: newlist sorted( listtobesorted, keylambda k: (kage, kname) ) or, likewise. Pretty cool stuff! Sorting a List of Dictionaries With Sort Function Note that since score is a string value, it needs to be converted to float for comparison. In other words, we create a tuple on the right side of the expression and unpack it on the left side of the expression. 4 Answers Sorted by: 11 You can sort by a tuple: sorted (l, keylambda k: (float (k 'score'), k 'id'), reverseTrue) This will sort by score descending, then id descending. To accomplish the swap, we leverage tuple packing and unpacking. Since looking into this topic, I’ve found that Python has a nice way of handling the variable swap in a single line of code: size = len(csv_mapping_list)Ĭsv_mapping_list, csv_mapping_list = csv_mapping_list, csv_mapping_listĬlearly, I didn’t pick that great of a variable name for the swap, but you get the idea. Let’s understand this by taking an example. In this article, we’ll learn how to sort them in a custom order. To do that, we leverage the “Age” field of each dictionary as seen in line 5. Sorting list of dictionaries by custom order in Python In the previous articles, we have discussed several ways of sorting dictionaries and lists of dictionaries. Here, we’ve sorted the list of dictionaries in place by age. If csv_mapping_list > csv_mapping_list:Ĭsv_mapping_list = csv_mapping_list Instead, we’ll leverage one of the more popular algorithms, selection sort: size = len(csv_mapping_list) Sorting is probably one of the most researched areas of Computer Science, so we won’t dive into the philosophy. Sort List by Dictionary values using emgetter () with sorted () This method uses the itemgetter () function from the operator module along with the sorted () function to sort the list based on the values of the dictionary. It’s normal for me to share a brute force method followed by a couple more elegant methods, so take care to skip ahead if needed. SolutionsĪs always, I like to share many possible solutions. Today, I want to focus on sorting a list of dictionaries. In any case, we always have to start with data processing. For instance, maybe older individuals prefer certain colors, or perhaps younger individuals have certain types of names. That way we could plot them in order of increasing or decreasing age to see if we could spot any trends. Using list.sort () Lists have only one special method: bash list.sort (, keyNone, reverseFalse) By default, sort () performs an A-Z-style sort, with lower values on the left. In this case, we might want to order our data points by age. You can use different function to sort different data types in Python. Likewise, order of the data might matter. In other words, we have our data, but we might want to use a subset of it. How to Sort a List of Dictionaries in Python: Sort and Sorted Written by Jeremy Grifski in Code Last Updated You may recall that I recently published an article on parsing a spreadsheet, and the output ended up being a list of dictionaries. Of course, having the data in a nice format and actually using that data for visualization are very different problems. Sorted(l, key=lambda x: x) = sorted(l, key=emgetter('name'))īoth techniques sort the list in the same order (verified by execution of the final statement in the code block), but the first one is a little faster.As mentioned before, I was working on parsing a CSV file for data visualization, and I ended up getting everything I wanted in the following format: csv_mapping_list = [ # Check that each technique produces the same sort order %timeit sorted(l, key=emgetter('name'))ġ0.7 µs ± 38.1 ns per loop (mean ± std. # Test the performance with itemgetter sorting on name %timeit sorted(l, key=lambda x: x)ġ3 µs ± 388 ns per loop (mean ± std. # Test the performance with a lambda function sorting on name Using the Pandas package is another method, though its runtime at large scale is much slower than the more traditional methods proposed by others: import pandas as pd
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