:=

Author: ahammadshawki8

python48 (walrus operator).py

@@ -0,0 +1,96 @@
+# walrus operator :=
+
+# there is a new syntax := that assigns values to variables as part of a larger expression.
+# It is known as the walrus operator.
+# This is the most controvercial feature of python3.8
+
+# this is desisgned to use inside expressions.
+# it actually assigns a variable to some part of the expression.
+
+# Example 1
+a = [0,1,2,3,4,5,6]
+
+if (n := len(a)) > 5:
+    print(f"List is too long ({n} elements, expected <= 5)")
+
+# what it does is that, it sets a variable n as the len(a) so that we can use it later on.
+# it helps avoid calling len() function twice.
+# But it doesn't effects the expression.
+# we must use brakets to distinguish the part of expression that we want to set as a var with walrus.
+
+
+# Example 2
+while (ans := input("Enter a number: ")) != "":
+    print(ans)
+
+# this operator is also helpful with while-loops that compute a value to test loop termination 
+# and then that same value again in the body of the loop.
+
+
+# Example 3
+names = ["1. ahammad", "2. cristiano", "3. ramos", "4. zidan"]
+allowed_names = ["ahammad", "cristiano", "marcelo"]
+
+walrus_list = [clean_name.title() for name in names if (clean_name := name[3:]) in allowed_names]
+print(walrus_list)
+
+# Another motivated use case of walrus operator in list comprehensions
+# where a value computed in a filtering condition isalso needed in the expression body.
+
+
+# Example 4
+# we can do all the stuffs without walrus which we can do with walrus.
+# the only advantage walrus gives us is to remove some extra line of codes.
+
+# Without Walrus
+x = 5
+without_walrus = x < 7
+print(without_walrus)
+
+# With Walrus
+x = 5
+print(walrus := x < 7) 
+# we can use the var later on
+print(not walrus)
+
+# Example 5
+# this is the best advantage of walrus operators. 
+# It is simmilar to example 2.
+
+# Without Walrus
+nums = []
+num = input("Type a number: ")
+while num.isdigit():
+    nums.append(int(num))
+    num = input("Type a number: ")
+print(nums)
+
+# With Walrus
+nums = []
+while (num := input("Type a number: ")).isdigit():
+    nums.append(num)
+print(nums)
+
+
+
+# Example 6
+# if helps us avoiding levels of indentation.
+
+# Without Walrus
+var = 5
+if var == 5:
+    ans = input("Enter your name: ")
+    if ans != "":
+        print("Nice name!")
+
+
+# With walrus
+var = 5
+if var == 5 and (ans := input("Enter your name: ")) != "":
+    print("Nice name") 
+
+
+# Now we know what is walrus and where should we use it.
+# It makes the code kind of hard to understand.
+# so, if we really want to implement it within our code and make our code DRY, then we can do thaat.
+# Otherwise, we can do the exact same things without the walrus operator :=