Python - Mapping Functions over Iterables: map


You can apply an operation to lists and other sequences for each item and collect the results.

The following code shows how to update all the counters in a list can be done easily with a for loop:


counters = [1, 2, 3, 4] 
updated = [] # from  w w w. j a  v a2  s .  co  m
for x in counters: 
    updated.append(x + 10)                 # Add 10 to each item 

print( updated )


Python provides built-ins that do most of the work.

The map function applies a function to each item in an iterable object and returns a list containing all the function call results.

For example:


counters = [1, 2, 3, 4] 
def inc(x): return x + 10                  # Function to be run 
# from  w  w  w .  ja  v a 2s .  c  o  m
d=list(map(inc, counters))                   # Collect results 
print( d )


Here, we map inc method on each list item and collects all the return values into a new list.

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