Introduction to the usage of python function enumerate

The enumerate function is used to traverse the elements in the sequence and their subscripts.

enumerate function description:

Function prototype: enumerate(sequence, [start=0])

Function: List the sequence data separately starting the loopable sequence sequence with start and data subscript

That is, for a traversable data object (such as a list, tuple, or string), enumerate will combine the data object into an index sequence and list the data and data subscript at the same time.

Example:

There is a sequence, and using enumerate on it will get the following results:

start sequence[0]

start+1 sequence [1]

start+2 sequence[2]......

Applicable version:

Python2.3+

Python2.x

Note: The start parameter has been added after python2.6

English explanation:

Return an enumerate object. sequence must be a sequence, an iterator, or some other object which supports iteration. The next() method of the iterator returned by enumerate() returns a tuple containing a count (from start which defaults to 0) and the values ​​obtained from iterating over sequence.

Code example:

The enumerate parameters are traversable variables, such as strings, lists, etc.; the return value is the enumerate class.

import string
s = string.ascii_lowercase
e = enumerate(s)
print s
print list(e)

The output is:

abcdefghij
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd'), (4, 'e'), (5, 'f'), (6, 'g'), (7, 'h'), (8, 'i'), (9, 'j')]

You can use enumerate when you need both index and value values.

In this example, line is a string containing 0 and 1. Find all 1s:

def xread_line(line):
  return((idx,int(val)) for idx, val in enumerate(line) if val != '0')
 
print read_line('0001110101')
print list(xread_line('0001110101'))

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