How to define iteration in for Loop in Python
In this article, the editor introduces in detail "how to define iteration in for cycle in Python". The content is detailed, the steps are clear, and the details are handled properly. I hope that this article "how to define iteration in for cycle in Python" can help you solve your doubts.
For cycle of Python
Python is a collection-based iteration.
For in: # is a collection of objects-- for example, lists or tuples. # body of the loop a = ['Cao Cao', 'print', 'equipment'] for i in a: print (I)
Output:
Cao Cao
Cymbals
Equipment
An iterable object that can be passed to the built-in Python function iter () for processing and returned as an iterator
Iter ('Cao Cao Yaoyi') # Stringiter (['Cao Cao', 'Yueji', 'Jiaoji']) # Listiter (('Cao Cao', 'Yueyi', 'Jieqi') # Tupleiter ({'Cao Cao', 'Yueji'}) # Setiter ({'Cao Cao': 1 "Dict": 2, "equipment": 3}) #
Objects that cannot be iterated
Iter (1) # IntegerTraceback (most recent call last): File ", line 1, in TypeError: 'int' object is not iterableiter (1.1) # FloatTraceback (most recent call last): File", line 1 In TypeError: 'float' object is not iterableiter (len) # Built-in functionTraceback (most recent call last): File ", line 1, in TypeError:' builtin_function_or_method' object is not iterable
An iterator is a value producer that produces continuous values from its associated iterable objects. The built-in function next () is used to get the next value from the iterator.
List_ = ['Cao Cao', 'itr', 'itr'] itr = iter (list_) itrnext (itr), 'Cao Cao' next (itr), 'next (itr)'
Use the built-in list (), tuple (), and set () functions to get all values from the iterator at once.
List_ = ['Cao Cao', 'Jiaoyi', 'Jiaojie'] itr = iter (list_) list (itr) ['Cao Cao', 'Jiaoyi', 'Jiaoqi'] itr = iter (list_) tuple (itr) ('Cao Cao', 'Jiaoyi', 'Jiaoqi') itr = iter (list_) set (itr) {'Jiaogui', 'Cao Cao', 'Jiaoyi'} traversing the dictionary
A dictionary traversal loop in which loop variables are assigned to dictionary keys.
D = {'Cao Cao': 1, 'equipment': 2, 'equipment': 3} for k in d: print (k)
Output:
Cao Cao
Cymbals
Equipment
The operation of accessing dictionary values
For k in d: print (d [k]) # output: # 1#2#3for v in d.values (): print (v) # output: # 1 / 2 / 3
Traverse the keys and values of the dictionary at the same time. The loop variable for is not limited to a single variable, but can be a tuple.
I, j = (1,2) print (I, j) 1 2for I, j in [(1,2), (3,4), (5,6)]: print (I, j)
Output:
1 2
3 4
5 6
The dictionary method items () effectively returns the list of key / value pairs as a tuple.
D = {'Cao Cao': 1, 'weapon': 2, 'equipment': 3} d.items () dict_items ([('Cao Cao', 1), ('bike', 2), ('Jia Jie', 3)]) d = {'Cao Cao': 1, 'Qing': 2,'Qi': 3} for k, v in d.items (): print ('k =', k,', v =', v)
Output:
K = Cao Cao, v = 1
K = recently, v = 2
K = equipment, v = 3
Range () function
Python provides a built-in range () function that returns an iteration that produces a sequence of integers.
Range () returns an iteration that produces an integer that begins with 0, up to but not including the numeric value
X = range (5) xrange (0,5) type (x)
Range objects are iterable, so you can iterate through them through for loops to get values.
For n in x: print (n)
Output:
0
one
two
three
four
List () and tuple () get the values of all the loop traverses at once.
List (x) [0,1,2,3,4] tuple (x) (0,1,2,3,4)
Range (,) returns an iteration result.
List (range (5, 20, 3)) [5, 8, 11, 14, 17] # defaults to 1list (range (5, 10, 1)) [5, 6, 7, 8, 9] list (range (5, 10)) [5, 6, 7, 8, 9] # the numerical range must be list (range (- 5, 5)) [- 5, 4,-3,-2,-1, 0, 1, 2, 3, 4] list (range (5) -5)) [] list (range (5,-5,-1)) [5, 4, 3, 2, 1, 0,-1,-2,-3,-4] break statement and continue statement
Break terminates the loop completely.
For i in ['Cao Cao', 'Fengyi', 'Jijie']: if'in I: break print (I)
Output:
Cao Cao
Continue terminates the current iteration and proceeds to the next iteration.
For i in ['Cao Cao', 'Fengyi', 'Jijie']: if'in I: continue print (I)
Output:
Cao Cao
Equipment
Else statement
The clause else of the for loop is similar to the use of the while loop.
For i in ['Cao Cao', 'Jiaoyi', 'Jijie']: print (I) else: print ('over.')
Output:
Cao Cao
Cymbals
Equipment
End.
Else will not be executed if the list is break by a statement.
For i in ['Cao Cao', 'Jiaoyi', 'Jijie']: if I = = 'thanks': break print (I) else: print ('over.')
Output:
Cao Cao
After reading this, the article "how to define iterations in for Loop in Python" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it yourself. If you want to know more about related articles, please follow the industry information channel.
