Built-in functions

Determining the length of sequences

The len() functions returns an integer with the length b of an argument. It works with strings, lists, tuples, and dictionaries.

l = [0,1,2,3]
print len(l) # → 4

Creating lists of integer numbers

The range function allows to create lists of numbers on-the-fly. There are two optional parameters for the start value and the step size.

l = range(4) # [0,1,2,3]
l = range(1,5) # [1,2,3,4]
l = range(2,9,2) # [2,4,6,8]
l = range(5,0,-1) # [5,4,3,2,1]

Summing up numbers

The sum of a list of integer or float numbers can be calculated by the sum() function.

l = [1,2,3,4]
print sum(l)

Enumerating elements of lists

The enumerate() function associates an integer number starting from zero to each element in a list. This is helpful in loops where an index variable is required.

fruits = ['apple','banana','orange']
for i, fruit in enumerate(fruits):
print i, fruit

Merging two lists

The zip() function associates the elements of two lists to a single list of tuple. Excess elements are ignored.

fruits = ['apple','banana','orange']
prices = [0.55, 0.75, 0.80, 1.23]

for fruit,price in zip(fruits,prices):
print fruit, price