How do I counter value in a for loop as part of my dictionary key-CodePudding

I am trying to create a for loop that adds keys and values to a dictionary every time it loops. The counter value of this for loop is part of the key name that gets added to the dictionary every time. How can I code this without defining a separate set for key values and assigning them to key values? or better said, how can I remove this line? "y.insert(i, "This is key number " str(i 1))"

Here is my current code:

Dic = {}
y = []
for i in range(0,4):
    y.insert(i, "This is key number "   str(i 1))
    Dic[y[i]] = "This is a constant value for all keys"

CodePudding user response：

You literally just insert the new items at the last position of the list (for which you should use append, but that's besides the point), just to then get the element at that index out of the list. Instead, you can just assign it to a temporary variable, without the list:

Dic = {}
for i in range(0,4):
    x = "This is key number "   str(i 1)
    Dic[x] = "This is a constant value for all keys"

Of course, you don't really need that variable either, you can just put the expression into the [...] (but it might be argued that the above is more readable):

Dic = {}
for i in range(0,4):
    Dic["This is key number "   str(i 1)] = "This is a constant value for all keys"

Which now can be directly translated to a dictionary comprehension:

Dic = {"This is key number "   str(i 1): "This is a constant value for all keys" for i in range(0,4)}

After a bit of cleanup (note: f-strings require newer versions of Python, but there are other ways to format the number into the string without concatenation):

dic = {f"This is key number {i 1}": "This is a constant value for all keys" for i in range(4)}

CodePudding user response：

If you want to stick with something close to your starting for loop, just do:

Dic = {}
for i in range(0,4):
    Dic[f"This is key number {i}"] = "This is a constant value for all keys"

CodePudding user response：

You can use the dict's fromkeys() method:

Dic = dict.fromkeys(map("This is key number {}".format,range(4)),"constant")

print(Dic)
{'This is key number 0': 'constant', 
 'This is key number 1': 'constant', 
 'This is key number 2': 'constant', 
 'This is key number 3': 'constant'}