- if statement
- while Loop
- for statement
- break and continue statements and else clauses in loops
- for and while exercises
In Python, elif is used instead of else if, so the keyword of if statement is: if elif else
- Each condition is followed by a colon:, which indicates the block of statements to be executed after the condition is met.
- Use indentation to divide statement blocks. Statements with the same number of indentation form a statement block together.
- There is no switch – case statement in Python.
if condition_1: statement_block_1 elif condition_2: statement_block_2 else: statement_block_3
age=19 tall=186 if age <= 0: print("You're not born yet!") elif age < 18: print("You're still a minor!") elif age: print("You're an adult!") if tall < 170: print("You lack nutrition!") elif tall: print("You have good nutrition!")
if nesting demonstration:
#Grade 5 num=int(input("Please enter a score:")) if num >=90: print('A') else: if num >= 80: print('B') else: if num >= 70: print('C') else: if num >=60: print('D') else: print('E')
In Python, there is no do while Loop
while condition: Execute statements
a=1 while a<10: print(a) a=a+2
Use Ctrl+c to exit the loop
Infinite loops are useful for real-time client requests on the server.
a=1 while a==1: num=int(input("Please enter a number:")) print("The numbers you enter are:",num)
while Else the block of statements that execute else when the conditional statement is false.
a=5 while a <16: print(a,"Less than 16") a=a+4 else: print(a,"Greater than or equal to 16")
Similar to the syntax of if statement, if there is only one statement in your while loop body, you can write the statement on the same line as while
while(1):print("Can't stop! Press quickly ctrl+c") print("Goodbye")
The Python for loop can traverse any sequence of items, such as a list or a string.
The general format is as follows:
for <variable> in <sequence>: <statements> else: <statements>
languages=["C","C++","Python","Perl"] for x in languages: print(x)
languages=["C","C++","Python","Perl"] for x in languages: if x == "Python": print("Python!") break print("Circular data", x) else: print("No circular data") print("End of cycle!")
- If you need to traverse a sequence of numbers, use the built-in range() function. It generates a sequence
for i in range(6): print(i)
- You can also use range to specify the value of the interval
for i in range(5,9): print(i)
- You can make range start with a specified number and specify different increments (even negative numbers, sometimes called 'steps')
for i in range(0,10,3): print(i)
for i in range(-1,-12,-3): print(i)
- Combine the run() and len() functions to traverse the index of a sequence
a=['Google', 'Baidu', 'Runoob', 'Taobao', 'QQ'] for i in range(len(a)): print(i,a[i])
- You can also use the range() function to create a list
- The break statement can jump out of the loop bodies of for and while. If you terminate from a for or while loop, any corresponding loop else block will not execute.
- The continue statement is used to tell Python to skip the remaining statements in the current loop block and continue to the next loop.
Use break in while:
m=5 while m> 0: m=m-1 if m == 2: break print(m) print("Loop end")
Use continue in while:
m=5 while m> 0: m=m-1 if m == 3: continue print(m) print("Loop end")
In python, for Else means that there is no difference between the statements in for and the ordinary ones. The statements in else will be executed after the normal execution of the loop (that is, for is not interrupted by break ing out) So is else.
for n in range(2,20): for x in range(2,n): if n % x == 0: print(n,'Be equal to',x,'*',n//x) break else: print(n,"Prime number")
Python pass is an empty statement to maintain the integrity of the program structure.
pass does nothing. It is generally used as a placeholder statement, as shown in the following example:
for x in "Kobe bryant": if x =='o': pass print("pass block") print(x) print("forever")
for i in range(1,11): for k in range(1,i): print(k,end=" ") print("\n")
i=1 while i <= 9:#Number of external loop control lines j=1 while j<=i:#Number of internal circulation control columns s=i*j print("%dx%d=%d"%(i,j,s),end=" ") j=j+1 print("")#Line feed i=i+1
m=int(input("First number:")) n=int(input("Second number:")) min=min(m,n) for i in range(1,min+1): if(m % i == 0 and n % i == 0): r=i k=int((m*n)/r) print("greatest common divisor:",r) print("Minimum common multiple:",k)