[Section III] Python Process Control Statements-if, while, for, break, continue

Directory:

I. Conditional JUDGMENT Statement-if

Two. Looping statements-while & for

Three. Break & Continue statement.

Four. Exercises

Body:

One, conditional judgment statement-if:
1) The first type of syntax:

If condition: code block

2) The second type of syntax:

If condition: content One content two else: content three content four

3) The third type of syntax:

If condition 1: code block elif Condition 2: code block elif Condition 3: code block else: code block

Note:
= and = =: An equal sign is an assignment, and two equals is a comparison.
True and false:

If True: #此处的结果如果为真, the first print is executed forever, and if the result here is False, the second print is executed. Print ("xxx") else:print ("xxx")

If judging condition:
1) True, False
2) 1 > 2 n1 > N2 N1 = = N2
3) name = = "Jack" or "name" = "Jenny"
4) Name! = "Jack"
5) name = = "Jack" and pwd = = "123"

Example:

#!/usr/bin/env python #! _*_ coding:utf-8 _*_ #import getpassusername = Raw_input ("username:") password = getpass.getpass ("Password:") if username = = "Yangbin" and Password = = "Yangbin": Print ("" "******info******: Username:%s Password:%s" ""% (US Ername,password)) else:print ("Input error.")

Second, loop statement-while & for
1, while loop statement:
Grammar:

While condition: code block # Executes the loop body if the condition is true. # If the condition is false, the loop body is not executed.

Example 1:

# The While Process Control statement is a dead loop and will not automatically exit unless manually intervened. Import time # Importing timer while True:print ("1") Time.sleep (1) # Set the timer to enter print once per second ( "End")

Example 2:

Import timen1 = truewhile N1: # N1 is true. Print ("1") time.sleep (1) n1 = False//n1 The second assignment is false, which jumps out of the while loop. Print ("End")

2, for Loop statement
Grammar:

For variable name in "Looping content": # fixed collocation. Xxx

Example 1:
#打印l, I,n,u,x.
Method 1:

N1 = "Linux" for I in Range (len (n1)): temp = n1[i] Print (temp)

Method 2:

N1 = "Linux" for I in N1:print (i)

Three, break & continue statements.

Break is used to terminate the loop, which jumps out of the current loop, and the code below the break statement is no longer executed;

Continue is used to jump out of this cycle and continue the next cycle;

Example 1:
# Print the number 1-10 and skip the number 7.

i = 0j = Truewhile J:i = i + 1 if i = = 7:continue elif i = = 11:break print (i)

Example 2:
#打印字母l, i,n,u,x, remove N,u.

N1 = "Linux" for i in n1:if i = = "N" or i = = "U": # Note here with or, not with and, because I cannot be both N and U. Continue # If it is break here, only print out l,i print (i)

Four, exercises
1, use while loop and for loop Output 1 2 3 4 5 6 8 9 10 respectively.
# while loop.

i = 0while I < 10:i + = 1 if i = = 7:continue print (i)

# for Loop.

For I in range (one): # range (11), which is 0-10 of these 11 numbers. If i = = 0 or i = = 7:continue print (i)

2. The and of all numbers of 1-100.
# while loop.

i = 1sum = 0while I <= 100:sum + = i i + = 1print ("1+2+3+4+...+100=%d"% sum)

i = 1sum = 0while True:sum + = i i + = 1 if i = = 101:breakprint (sum)

# for Loop.

sum = 0for i in range (101): if i = = 0:continue sum + = IPrint ("1+2+3+4+...+100=%d"% sum)

3. All odd numbers in output 1-100
# while loop.

i = 0sum = 0while I < 100:i + = 1 if I% 2! = 0:sum + iprint ("1+3+5+...+99=%d"% sum)

# for Loop.

sum = 0for I in range: if i = = 0:continue elif I% 2! = 0:sum + iprint ("1+3+5+...+99=%d"% sum )

4. All even numbers in output 1-100
# while loop.

i = 1sum = 0while I <= 100:if I% 2 = = 0:sum + I i + = 1print ("2+4+6+...+100=%d"% sum)

# for Loop.

sum = 0for i in range (101): if i = = 0:continue Elif I 2 = = 0:sum + iprint ("2+4+6+...+100=%d"% su M

5, Beg 1-2+3-4+5 ... 99 of all numbers of the and
# while loop.

i = 0s = 0y = 0while I < 99:i + = 1 if I% 2! = 0:s + = i elif i% 2 = = 0:y = Isum = s + ypri NT ("1-2+3-4+5-6...-98+99=%d"% sum)

# for Loop.

s = 0y = 0for I in range: if i = = 0:continue elif I% 2! = 0:s + = i elif i% 2 = = 0: Y-= Isum = s + yprint ("1-2+3-4+5-6...-98+99=%d"% sum)

6. User Login (three chance retry)
# while loop.

Import Getpassi = 0while True:name = input ("Please input your name:") Password = getpass.getpass ("Please input your        Password: ") i + = 1 if name = =" Yangbin "and Password = =" Yangbin ": Print (" Login succeed! ") Break Else:print ("Your only input%d count"% (3-i)) if i = = 3:break

# for Loop.

Import getpassfor I in range (3): name = input ("Please input your name:") Password = getpass.getpass ("Please input y        Our password: ") if name = =" Yangbin "and Password = =" Yangbin ": Print (" Login succeed! ") Break Else:print ("Your only input%d count"% (2-i)) if i = = 2:break

The third section is complete!

This article is from the "Yangbin" blog, make sure to keep this source http://13683137989.blog.51cto.com/9636221/1896118

[Section III] Python Process Control Statements-if, while, for, break, continue