How do you get the number of rows in a pandas DataFrame?

Use len(df) or df.shape[0]. df.shape returns the rows and the columns together, and df["col"].count() counts only the values that are not empty.

Why does len() give TypeError: object of type 'int' has no len()?

Numbers have no length, so len(42) fails. To count digits, convert the number to text first: len(str(42)) returns 2. The same error with NoneType means the variable is None.

How do you count how many times a value appears in a list?

Use the list method count(): [3, 8, 8, 5, 3].count(8) returns 2. To count the items that meet a condition, use sum(1 for n in nums if n > 4).

How do you count unique items in a Python list?

Convert the list to a set and take its length: len(set([3, 8, 8, 5, 3])) returns 3, because a set keeps each value only once.

Why does len() of a nested list return fewer items than expected?

len() only counts the top level. [[1, 2], [3, 4, 5]] has a length of 2. To count every item inside, use sum(len(x) for x in nested).

How do you check if a list is empty in Python?

Write if not my_list:. An empty list counts as False, so the block runs only when the list has no items. if len(my_list) == 0: also works, but the first form is the usual style.

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How to Get the Length of a List in Python?

Q: How do you get the length of a list in Python?

Use the built-in len() function. len(["apple", "banana", "cherry"]) returns 3 and len([]) returns 0. Python lists have no .length property or .len() method.

Count the items of any list with len(), check if it is empty, count nested lists and unique values, and fix the errors you will meet along the way.

6 min readLast updated Nov 10, 2026

How do you get the length of a list in Python?

Short answer: use the built-in len() function. len(fruits) returns how many items the list has. An empty list returns 0.

python

fruits = ["apple", "banana", "cherry"]
 
print(len(fruits))   # 3
print(len([]))       # 0

Lists have no .length property and no .len() method like in other languages. In Python you always write len(my_list).

len() counts the items of a list, returns 0 when it is empty, only counts the top level of a nested list and fails with numbers.

Every way to count items in Python

What you want	Code	Result
Items in a list	`len(["apple", "banana", "cherry"])`	`3`
Check if a list is empty	`if not fruits:`	`True` when empty
Every item in a nested list	`sum(len(x) for x in [[1, 2], [3, 4, 5]])`	`5`
Unique items	`len(set([3, 8, 8, 5, 3]))`	`3`
How many times a value appears	`[3, 8, 8, 5, 3].count(8)`	`2`
Items that meet a condition	`sum(1 for n in nums if n > 4)`	`3`
Characters in a string	`len("hello")`	`5`
Keys in a dict, items in a tuple or set	`len({"a": 1, "b": 2})`, `len((1, 2, 3))`	`2`, `3`
Rows of a pandas DataFrame	`len(df)` or `df.shape[0]`	Number of rows
Elements of a NumPy array	`arr.size` (all), `len(arr)` (first dimension)	`6`, `2`

Use len() with lists

len() works with any list, whatever the items are. It counts items, not values, so None, "" and 0 also count:

python

print(len([1, None, "", 0]))   # 4

The length changes when you add or remove items:

python

fruits = ["apple", "banana", "cherry"]
 
fruits.append("kiwi")
print(len(fruits))   # 4
 
fruits.pop()
print(len(fruits))   # 3

len() is instant even with millions of items, because Python keeps the size stored in the list. You don't need to save it in a variable to make your code faster.

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Use the length to reach items by position

Positions start at 0, so the last item is at len(fruits) - 1. Asking for fruits[len(fruits)] fails:

python

fruits = ["apple", "banana", "cherry"]
 
print(fruits[len(fruits) - 1])   # cherry
print(fruits[-1])                # cherry, the short way
print(fruits[len(fruits)])       # IndexError: list index out of range

To loop with the position, enumerate() is clearer than range(len(...)):

python

for i, fruit in enumerate(fruits):
    print(i, fruit)
# 0 apple
# 1 banana
# 2 cherry

Check if a list is empty

An empty list counts as False, so you don't need len():

python

cart = []
 
if not cart:
    print("empty")   # empty

if len(cart) == 0: also works, but if not cart: is the usual style in Python.

Count the items in a nested list

len() only counts the top level. A list with two lists inside has a length of 2, however many items each one has:

python

nested = [[1, 2], [3, 4, 5]]
 
print(len(nested))                    # 2
print(sum(len(x) for x in nested))    # 5

If the lists can go deeper, use a small recursive function:

python

def count_all(items):
    return sum(count_all(x) if isinstance(x, list) else 1 for x in items)
 
print(count_all([1, [2, [3, 4]], 5]))   # 5

Count unique values, repeats and matches

python

nums = [3, 8, 8, 5, 3]
 
print(len(set(nums)))                # 3  unique values
print(nums.count(8))                 # 2  times 8 appears
print(sum(1 for n in nums if n > 4)) # 3  items greater than 4

len() with strings, dicts, tuples, sets and ranges

len() works with every Python collection:

python

print(len("hello"))            # 5  characters
print(len({"a": 1, "b": 2}))   # 2  keys
print(len((1, 2, 3)))          # 3
print(len({1, 2, 2, 3}))       # 3  sets drop repeats
print(len(range(10)))          # 10

Your own classes can work with len() too. Define a __len__ method that returns an integer.

Length in NumPy and pandas

python

import numpy as np
import pandas as pd
 
arr = np.array([[1, 2, 3], [4, 5, 6]])
print(len(arr))     # 2  rows (first dimension)
print(arr.size)     # 6  every element
print(arr.shape)    # (2, 3)
 
df = pd.DataFrame({"name": ["Ana", "Luis", "Eva"]})
print(len(df))      # 3  rows
print(df.shape)     # (3, 1)  rows and columns

In pandas, len() counts every row, including empty values. df["col"].count() counts only the values that are not empty.

Use AI to work with list lengths

An assistant like ChatGPT, Claude or GitHub Copilot can explain an error or write the counting code for your data. These three prompts are ready to copy.

1. Explain an error

In Python, this line: [paste your line]
gives this error: [paste the error].
Explain why and show me how to fix it.

2. Count what you need

I have this Python list: [paste a short example].
Show me how to count [all the items / the unique items / the items that ...]
and explain each line.

3. Check a dataset

I have a pandas DataFrame with these columns: [list the columns].
Show me how to count the rows, the empty values in each column
and the rows where [your condition].

Run every answer yourself and check the numbers with a small example you can count by hand.

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Common problems with list length in Python

What you see	Why it happens	Fix
`AttributeError: 'list' object has no attribute 'length'`	Python lists have no `.length`	Use `len(my_list)`
`AttributeError: 'list' object has no attribute 'len'`	`len` is a function, not a method	Write `len(my_list)`, not `my_list.len()`
`TypeError: object of type 'int' has no len()`	Numbers have no length	Use `len(str(number))` to count digits
`TypeError: object of type 'NoneType' has no len()`	The variable is `None`, often from a function with no `return`	Check the value, or use `len(items or [])`
`TypeError: object of type 'generator' has no len()`	Generators don't know their size	`len(list(gen))` or `sum(1 for _ in gen)`
`IndexError: list index out of range`	The last position is `len(list) - 1`	Use `my_list[-1]` or `range(len(my_list))`
`len()` of a nested list is smaller than expected	It only counts the top level	`sum(len(x) for x in nested)`

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Python list length in a 2-page cheat sheet

len(), empty lists, nested lists, unique values and matches, len() with other collections, NumPy and pandas, common errors and prompts for ChatGPT, Claude or Copilot. Free, in PDF.

Python list length cheat sheet

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Every way to count items in a list
How to count nested lists, unique values and matches
Common errors and prompts to solve them with AI

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Frequently asked questions about Python list length

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How to Get the Length of a List in Python?

How do you get the length of a list in Python?

Every way to count items in Python

Use len() with lists

You already count items in Python, now build with AI

Use the length to reach items by position

Check if a list is empty

Count the items in a nested list

Count unique values, repeats and matches

len() with strings, dicts, tuples, sets and ranges

Length in NumPy and pandas

Use AI to work with list lengths

From Python lists to AI applications

Common problems with list length in Python

Related guides

Python list length in a 2-page cheat sheet

Frequently asked questions about Python list length

How do you get the number of rows in a pandas DataFrame?

Why does len() give TypeError: object of type 'int' has no len()?

How do you count how many times a value appears in a list?

How do you count unique items in a Python list?

Why does len() of a nested list return fewer items than expected?

How do you check if a list is empty in Python?

How do you get the length of a list in Python?