Python Lambda
A lambda function is a small anonymous function.
A lambda function can take any number of arguments, but can only have one expression.
Syntax
lambda arguments : expression
The expression is executed and the result is returned:
Example
Add 10 to argument a, and return the result:
x = lambda a : a + 10
print(x(5))
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Lambda functions can take any number of arguments:
Example
Multiply argument a with argument b and return the result:
x = lambda a, b : a * b
print(x(5, 6))
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Example
Summarize argument a, b, and c and return the result:
x = lambda a, b, c : a + b + c
print(x(5, 6, 2))
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Why Use Lambda Functions?
The power of lambda is better shown when you use them as an anonymous function inside another function.
Say you have a function definition that takes one argument, and that argument will be multiplied with an unknown number:
def myfunc(n):
return lambda a : a * n
Use that function definition to make a function that always doubles the number you send in:
Example
def myfunc(n):
return lambda a : a * n
mydoubler = myfunc(2)
print(mydoubler(11))
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Or, use the same function definition to make a function that always triples the number you send in:
Example
def myfunc(n):
return lambda a : a * n
mytripler = myfunc(3)
print(mytripler(11))
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Or, use the same function definition to make both functions, in the same program:
Example
def myfunc(n):
return lambda a : a * n
mydoubler = myfunc(2)
mytripler = myfunc(3)
print(mydoubler(11))
print(mytripler(11))
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Use lambda functions when an anonymous function is required for a short period of time.
