What is a lambda expression?
Esercitarsi con le domande di colloquio di coding in Python
Kirill Smirnov
Data Science Consultant, Altran
Definition
lambda expression/function - is a short function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
Definition
lambda expression/function - is a short function having the following syntax:
lambda
Definition
lambda expression/function - is a short function having the following syntax:
lambda arg1, arg2, ...:
Definition
lambda expression/function - is a short function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
lambda x: x**2
squared = lambda x: x**2squared(4)
16
4 $\rightarrow$ x $\rightarrow$ x**2 $\rightarrow$ 16
Definition
lambda expression/function - is a short function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
power = lambda x, y: x**ypower(2, 3)
8
2, 3 $\rightarrow$ x, y $\rightarrow$ x**y $\rightarrow$ 8
Missing argument
power = lambda x, y: x**y
power(2)
TypeError
Comparison to normal function definition
squared_lambda = lambda x: x**2
def squared_normal(x):
return x**2
Comparison to normal function definition
lambda
def
Comparison to normal function definition
squared_lambda = lambda
def squared_normal
Comparison to normal function definition
squared_lambda = lambda x:
def squared_normal(x):
Comparison to normal function definition
squared_lambda = lambda x: x**2
def squared_normal(x):
return x**2
squared_lambda(3)
9
squared_normal(3)
9
Passing lambda function as an argument
def function_with_callback(num, callback_function):
return callback_function(num)
callback_function(arg) - a function with one argument
def squared_normal(x):
return x**2
function_with_callback(2, squared_normal)
4
Passing lambda function as an argument
def function_with_callback(num, callback_function):
return callback_function(num)
callback_function(arg) - a function with one argument
--> def squared_normal(x): <--
--> return x**2 <--
--> function_with_callback(2, squared_normal) <--
4
Passing lambda function as an argument
def function_with_callback(num, callback_function):
return callback_function(num)
callback_function(arg) - a function with one argument
function_with_callback(2, lambda x: x**2)
4
Definition
lambda expression/function - is a short function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
Definition
lambda expression/function - is a short (anonymous) function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
squared = lambda x: x**2
squared(3)
9
Definition
lambda expression/function - is a short (anonymous) function having the following syntax:
lambda arg1, arg2, ...: expression(arg1, arg2, ...)
(lambda x: x**2)(3)
9
Ternary operator
def odd_or_even(num):
if num % 2 == 0:
return 'even'
else:
return 'odd'
odd_or_even(3)
'odd'
odd_or_even(6)
'even'
Ternary operator
def odd_or_even(num):
return 'even' if num % 2 == 0 else 'odd'
odd_or_even(3)
'odd'
odd_or_even(6)
'even'
Ternary operator
odd_or_even = lambda num: 'even' if num % 2 == 0 else 'odd'
odd_or_even(3)
'odd'
odd_or_even(6)
'even'
Practical use
Use lambda expressions when it is really necessary!
- within function bodies to perform a small task
- as callbacks
Let's practice!
Esercitarsi con le domande di colloquio di coding in Python
