10 Python Comprehensions You SHOULD Be Using
Description
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Notes
00:00 Introduction to Python Comprehensions
- Video covers 10 Python comprehensions progressing in difficulty
- 00:10 Starting with basic list comprehension
00:12 Basic List Comprehension
- 00:15 Traditional approach: loop through range and append to list
- 00:33 List comprehension syntax:
[x for x in range(10)]- Faster and more readable than traditional loops
- Expression on left (what gets added), for loop on right
- 01:36 Modifying the expression:
[x + 1 for x in range(10)]produces values 1-10
02:06 List Comprehension with Filtering
05:20 Complex Filtering with Multiple Conditions
for string in options:
if len(string) <= 1:
continue
if string[0] != "a":
continue
if string[-1] != "y":
continue
valid_strings.append(string)
print(valid_strings)
- Filter strings starting with 'A' and ending with 'Y'
- Check string length >= 2
- Verify first character equals 'A'
- Verify last character equals 'Y'
Complex Filtering with Comprehensions
valid_strings = [
string
for string in options
if len(string) >= 2
if string[0] == "a"
if string[-1] == "y"
]
print(valid_strings)
07:42 Nested List Comprehension
for row in matrix:
for num in row:
flattened.append(num)
- 07:47 Flattening a matrix (2D list into 1D list)
- Syntax:
[num for row in matrix for num in row] - First for loop is exterior, subsequent loops are interior
- Interior loops execute for each iteration of exterior loop
- Syntax:
With Comprehensions
flattened = [num for row in matrix for num in row]
- 09:07 Can chain multiple for loops but becomes confusing with more than 2-3
09:19 If-Else Logic in Comprehensions
for number in range(10):
if number % 2 == 0:
categories.append("Even")
else:
categories.append("Odd")
- 09:26 Categorizing numbers as "even" or "odd"
- Syntax:
[("even" if x % 2 == 0 else "odd") for x in range(10)] - Expression on left determines value to add (not for filtering)
- Ternary operator (if-else) works on left side of comprehension
- Syntax:
categories = [
"Even" if x % 2 == 0 else "Odd" for x in range(10)
]
11:24 Building Multidimensional Lists
import pprint
lst = []
for a in range(5):
l1 = []
for b in range(5):
l2 = []
for num in range(5):
l2.append(num)
l1.append(l2)
lst.append(l1)
print(lst)
- 11:36 Creating 5Ă—5Ă—5 3D matrix
- Traditional approach uses nested loops and append operations
12:31 Comprehension approach
lst = [[[num for num in range(5)] for _ in range(5)] for _ in range(5)]
- Anonymous variable
_used when iteration variable not needed - 13:32 Reading nested comprehensions: find first for loop, check left side to understand what's added at each level
14:35 Functions in Comprehensions
- Apply function to values:
[square(x) for x in range(10)] - Function calls work on left side for transformation
- Function calls can be used in filtering conditions too
- Clean variable names make complex comprehensions readable
15:40 Dictionary Comprehension
pairs = [("a", 1), ("b", 2), ("c", 3)]
my_dict = {k: v for k, v in pairs}
print(my_dict)
# {'a': 1, 'b': 2, 'c': 3}
16:49 Set Comprehension
nums = [1, 2, 2, 3, 3, 3, 4, 4, 4, 4]
unique_squares = {x**2 for x in nums}
# {16, 1, 4, 9}
# REMEMBER that Python sets are non-ordered
17:49 Generator Comprehension (Advanced)
sum_of_squares = sum(x**2 for x in range(1000000))
- 18:05 Summing squares from 0 to 1 million without storing all values
- Generator syntax (parentheses):
sum(x**2 for x in range(1000000)) - Generates values on-demand rather than pre-generating entire list
- Generator syntax (parentheses):
- 18:12 Memory efficient: only stores current value, not all 1 million values
- 20:31 Using list brackets instead of parentheses creates list comprehension (stores all values in memory)
- 21:14 Recommended to learn more about generators and iterators
10 Python Comprehensions You SHOULD Be Using
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Description
Notes
00:00 Introduction to Python Comprehensions
00:12 Basic List Comprehension
02:06 List Comprehension with Filtering
05:20 Complex Filtering with Multiple Conditions
Complex Filtering with Comprehensions
07:42 Nested List Comprehension
With Comprehensions
09:19 If-Else Logic in Comprehensions
11:24 Building Multidimensional Lists
12:31 Comprehension approach
14:35 Functions in Comprehensions
15:40 Dictionary Comprehension
16:49 Set Comprehension
17:49 Generator Comprehension (Advanced)