author ： Han Xinzi @ShowMeAI
Tutorial address ：http://www.showmeai.tech/tutorials/56
This paper addresses ：http://www.showmeai.tech/article-detail/72
Statement ： copyright , For reprint, please contact the platform and the author and indicate the source
Python There are many sequential data structures in （ Such as list or string ）, have access to for Loop through .
grammar ：
for The syntax of the loop is as follows ：
for iterating_var in sequence: statements(s)
flow chart ：
Code instance （ The code can be in On-line python3 Environmental Science Run in ）
for letter in 'ShowMeAI': # First instance
print(" The current letter : %s" % letter)
fruits = ['banana', 'apple', 'mango']
for fruit in fruits: # Second example
print(' Current fruit : %s'% fruit)
print(" complete !")The output of the above code :
The current letter : S The current letter : h The current letter : o The current letter : w The current letter : M The current letter : e The current letter : A The current letter : I Current fruit : banana Current fruit : apple Current fruit : mango complete !
Another way to do loop traversal is through the index , The following example （ The code can be in On-line python3 Environmental Science Run in ）：
fruits = [' Banana ', ' Apple ', ' grapes ']
for index in range(len(fruits)):
print(' Current fruit : %s' % fruits[index])
print(" complete !")The output of the above code ：
Current fruit : Banana Current fruit : Apple Current fruit : grapes complete !
In the above example, we use the built-in function len() and range(), function len() Returns the length of the list , That is, the number of elements . range Returns the number of a sequence .
stay python in ,for … else That means ,for There is no difference between the sentences in and the ordinary ones ,else The statement in will be executed normally in the loop （ namely for Not through break Jump out and interrupt ） In case of execution ,while … else Is the same .
for num in range(20,30): # iteration 10 To 20 Number between
for i in range(2,num): # Iterate over the factors
if num%i == 0: # Determine the first factor
j=num/i # Calculate the second factor
print ('%d be equal to %d * %d' % (num,i,j))
break # Jump out of current loop
else: # Cyclic else part
print ('%d It's a prime number ' % num)The output of the above code ：
20 be equal to 2 * 10 21 be equal to 3 * 7 22 be equal to 2 * 11 23 It's a prime number 24 be equal to 2 * 12 25 be equal to 5 * 5 26 be equal to 2 * 13 27 be equal to 3 * 9 28 be equal to 2 * 14 29 It's a prime number
Let's use what we learned for loop , Draw different patterns , Help you get familiar with for Use circularly
The code can be in On-line python3 Environmental Science Run in .
rows = int(input(' Enter the number of columns ： '))
print(" Print a hollow equilateral triangle , Here, take out if-else Conditional judgment is solid ")
for i in range(0, rows + 1):# Variable i Control the number of lines
for j in range(0, rows - i):#(1,rows-i)
print(" ", end='')
j += 1
for k in range(0, 2 * i - 1):#(1,2*i)
if k == 0 or k == 2 * i - 2 or i == rows:
if i == rows:
if k % 2 == 0:# Because the first number is from 0 At the beginning , So if you print even numbers *, Odd print spaces
print("*", end='')
else:
print(" ", end='')# Notice the ", end='' ", Must not omit , Can play the role of not breaking lines
else:
print("*", end='')
else:
print(" ", end='')
k += 1
print("\n")
i += 1The code can be in On-line python3 Environmental Science Run in .
rows = int(input(' Enter the number of columns ： '))
print(" Print a diamond shape such as a hollow , Here, take out if-else Conditional judgment is solid ")
rows = int(input(' Enter the number of columns ： '))
for i in range(rows):# Variable i Control the number of lines
for j in range(rows - i):#(1,rows-i)
print(" ", end='')
j += 1
for k in range(2 * i - 1):#(1,2*i)
if k == 0 or k == 2 * i - 2:
print("*", end='')
else:
print(" ", end='')
k += 1
print("\n")
i += 1
# The bottom half of the diamond
for i in range(rows):
for j in range(i):#(1,rows-i)
print(" ", end='')
j += 1
for k in range(2 * (rows - i) - 1):#(1,2*i)
if k == 0 or k == 2 * (rows - i) - 2:
print("*", end='')
else:
print(" ", end='')
k += 1
print("\n")
i += 1Please click to B I'm looking at it from the website 【 Bilingual subtitles 】 edition
https://www.bilibili.com/video/BV1yg411c7Nw
The code for this tutorial series can be found in ShowMeAI Corresponding github Download , Can be local python Environment is running , Babies who can visit foreign websites can also directly use google colab One click operation and interactive operation learning Oh ！
This tutorial series covers Python The quick look-up table can be downloaded and obtained at the following address ：
