Introduce four python functions that are commonly used by great gods but not commonly used by you
Introduce four python functions that are commonly used by great gods but not commonly used by you
Https://mp.weixin.qq.com/s/C2nw4JShmj1FlLeDy0IeRA
Today, we will talk about four functions: assert, map,filter,reduce.
Assert
Commonly known as assertion! That is to say, to assert a thing, if it is true, the program will continue; if it is false, an error will be reported.
How to use it?
Two uses
Assert
Assert
First kind
Def avg (marks):
Assert len (marks)! =
Return sum (marks) / len (marks)
Mark1 = []
Print ("Average of mark1:", avg (mark1))
The result is
AssertionError
The second kind
Def avg (marks):
Assert len (marks)! =, "List is empty."
Return sum (marks) / len (marks)
Mark2 = [55, 88, 78, 90, 79]
Print ("Average of mark2:", avg (mark2))
Mark1 = []
Print ("Average of mark1:", avg (mark1))
The result is
Average of mark2: 78.0
AssertionError: List is empty.
Map
In many cases, we perform the same operation on the data in a list, such as:
Items = [1,2,3,4,5]
Squared = []
For i in item s:
Squared. Append (iTunes * 2)
At this point, you can use map operation in the format:
Map (function_to_apply, list_input)
The specific operation is
Items = [1,2,3,4,5]
Squared = list (map (lambda x: Xerox * 2, items))
Of course, functions can be put in list.
Def multiply (x):
Return (xonomx)
Def add (x):
Return (xonomx)
Funcs = [multiply, add]
For i in range (5):
Value = list (map (lambda x: X (I), funcs))
Print (value)
# Output:
# [0, 0]
# [1, 2]
# [4, 4]
# [9, 6]
# [16, 8]
Of course, you can also perform str2id operations.
A = ['5','2','3','4','5']
Print (list (map (int, a)
# [5, 2, 3, 4, 5]
Filter
The filter function is to filter and filter a given condition.
Number_list = range (- 5,5)
Less_than_zero = list (filter (lambda x: X)
