One-Liners

1) Multiple Variable Assignment

# Traditional way
a = 1
b = "ok"
c = False
 
# Pythonic way
a, b, c = 1, "ok", False
 
# Result
print(a, b, c)
# Show: 1 ok False

2) Variable Swap

# Traditional way
a = 1
b = "ok"
 
c = a
a = b
b = c
 
# Pythonic way
a, b = 1, "ok"
a, b = b, a
 
# Result
print(a, b)
# Shows: ok 1

# Pythonic way
a, b, c, d = 1, "ok", True, ["i", "j"]
a, b, c, d = c, a, d, b
 
# Result
print(a, b, c, d)
# Shows: True 1 ["i", "j"] ok

3) Variable Conditional Assignment

x = 3
 
# Traditional way
if x % 2 == 1:
    result = f"{x} is odd"
else:
    result = f"{x} is even"
 
# Pythonic way
result = f"{x} " + ("is odd" if x % 2 == 1 else "is even")
 
# Result
print(result)
# Shows: 3 is odd

4) Presence of a Value in a List

pet_list = ["cat", "dog", "parrot"]
 
# Traditional way
found = False
for item in my_list:
    if item == "cat":
        found = True
        break
 
# Pythonic way
found = "cat" in pet_list
 
# Result
print(found)
# Shows: True

pet_dict = {"cat": "Mitchi", "dog": "Max", "parrot": "Pepe"}
found = "cat" in pet_dict
print(found)
# Shows: True

5) Operations on Lists

my_list = [1, 2, 3, 4, 5]
 
# Traditional way
max_value = 0
for value in my_list:
    if value > max_value:
        max_value = value
 
# Pythonic way
max_value = max(my_list)
 
# Result
print(max_value)
# Shows: 5

6) List Creation with Duplicate Values

size = 10
 
# Traditional way
my_list = []
for i in range(size):
    my_list.append(0)
 
# Pythonic way
my_list = [0] * size
 
# Result
print(my_list)
# Shows: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

my_list = [1, 2] * 5

# Result: [1, 2, 1, 2, 1, 2, 1, 2, 1, 2]

my_tuple = (1, 2) * 5
print(my_tuple)
# Shows: (1, 2, 1, 2, 1, 2, 1, 2, 1, 2)

7) List Creation with Sequential Values

count = 10
 
# Traditional way
my_list = []
for i in range(count):
    my_list.append(i)
 
# Pythonic way
my_list = list(range(count))
 
# Result
print(my_list)
# Shows: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# List with odd values
my_list = list(range(1, 10, 2))
print(my_list)
# Shows: [1, 3, 5, 7, 9]

# List with descending values and negative values
my_list = list(range(5, -5, -1))
print(my_list)
# Shows: [5, 4, 3, 2, 1, 0, -1, -2, -3, -4]

my_set = set(range(count))
my_tuple = tuple(range(count))
 
# Result
print(my_set)
# Shows: {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
print(my_tuple)
# Shows: (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

8) List Creation with a Loop

count = 4
 
# Traditional way
my_list = []
for i in range(count):
    my_list.append(count**i)
 
# Pythonic way
my_list = [count**x for x in range(count)]
 
# Result
print(my_list)
# Shows: [1, 4, 16, 64]

my_set = set(count**x for x in range(count))
print(my_set)
# Shows: {1, 4, 16, 64}

squares = [i * i for i in range(5)]
# [0, 1, 4, 9, 16]

squares = [i * i for i in range(5) if i % 2 == 0]
# [0, 4, 16]

9) List Creation with Conditions if-else

users = [("Megan", 56),
("Karen", 32),
("Chad", 28),
("Brent", 44)]

# Traditional way
young_users = []
for user in users:
    if (user[1] < 35):
        young_users.append(user[0])
 
# Pythonic way
young_users = [x for x, y in users if y < 35]
 
# Result
print(young_users)
# ["Karen", "Chad"]

var = 42 if 3 > 2 else 999
# 42

10) Reading a File Line by Line

# Traditional way
lines = []
with open(filename) as file:
    for count, line in enumerate(file):
        lines.append(f"Line {count + 1}: " + line.strip())
 
# Pythonic way
with open(filename) as file:
    lines = [f"Line {count + 1}: " + line.strip() for count, line in enumerate(file)]

my_list = [line.strip() for line in open('filename.txt', 'r')]

11) Print without new lines

# No need to do this:
data = [0, 1, 2, 3, 4, 5]
for i in data:
    print(i, end=" ")
print()

# One-liner
print(*data)
# 0 1 2 3 4 5

12) Days left in year

import datetime;print((datetime.date(2023,1,1)-datetime.date.today()).days)
# 36

>> python -c "import datetime;print((datetime.date(2023,1,1)-datetime.date.today()).days)"
36

>> alias daysleft='python -c "import datetime;print((datetime.date(2023,1,1)-datetime.date.today()).days)"'

>> daysleft
36

13) Reversing a List

a = [1, 2, 3, 4, 5, 6]
a = a[::-1]
# [6, 5, 4, 3, 2, 1]

14) 以空白做區隔的數字字串，轉換成整數 List

user_input = "1 2 3 4 5 6"

my_list = list(map(int, user_input.split()))
# [1, 2, 3, 4, 5, 6]