Python Learning Note __3.2 iteration

# This is a learning note for the Liaoche teacher Python tutorial

1. Overview

Given a list or tuple, we can traverse the list or tuple through a for loop, which we call iteration (iteration).

of course, not only list and tuple can iterate. as long as it is an iterative object, there can be iterations, whether or not the subscript is available. including Dict, str, generator

in Python, an iteration is done through a for ... in. .

1.1, the iteration of the dictionary

# define a dictionary

D = {' A ': 1, ' B ': 2, ' C ': 3}

Key of an iterative dictionary

For key in D:

The value of the iteration dictionary

For value in D.values ():

Iterative key-value pairs

For K, V in d.items ()

1.2. String iteration

For ch in ' ABC ':

1.3. List Iteration

# define a list

l=[1,2,3]

Subscript of the Iteration list

For I in L:

Print (l.index (i))

The value of the iteration list

For in L:

Print (i)

The index of the iteration list and the element itself

For I, value in enumerate (L): # Enumerate function can turn a list into an index-element pair C7>for i in L:

Print (L.index (i), i)

Two iterations of a variable

For x, y in [(1, 1), (2, 4), (3, 9)]:

2. Examples

Write a function that uses iterations to find the minimum and maximum values in a list and return a tuple:

#-*-Coding:utf-8-*-

def findminandmax (L):

If Len (L) ==0:

Return (none, none)

MIN=L[0]

MAX=L[0]

For value in L:

If value > Max:

Max=value

Elif Value < min:

Min=value

Return Min,max

Python Learning Note __3.2 iteration