Python Basics--04 Flow control statements

1.Python Indentation Rules

Preferably four spaces, followed by tab, no spaces tab mixed

2.Python Flow Control Statement code block principle

: represents the beginning of a code block

If you hit the code in a Python interactive environment, also pay special attention to indentation, and exit indentation requires more than one line of return

3.if Statement 3.1 Ordinary if statement

>>> age=20
>>> if age >=18:
... print ' Your is ', age
... print ' Aduit '
...
Your age is 20
Aduit

3.2if-else statements

Note:else there is a ":" later.

>>> if age >= 18:
... print ' Aduit '
.. else:
... print ' teenager '
...
Aduit

3.3if-elif-else statements

If-elif statement and multi-if statement differences

If-elif condition judgment will be judged from top to bottom, if a certain judgment is True, after executing the corresponding code block, the subsequent condition judgment is ignored and no longer executed.

The multi-if statement is executed all, even if the preceding conditions are met.

>>> if age >=18:
... print ' Aduit '
... elif age >=6:
... print "Teenager"
... elif age >=3:
... print ' Kid '
.. else:
... print ' baby '
...
Aduit

4. Looping statements 4.1for Loops

>>> l= [' Adam ', ' Lisa ', ' Bart ']

>>> for name in L:

... print Name

4.2While Loops

>>> n=10

>>> x=0

>>> while X<n:

... print X

... x+=1

4.3break Exit Loop

>>> sum = 0

>>> x=1

>>> while True:

... sum+=x

... x+=1

... if x>100:

... break

4.4continue Continue looping

>>> l=[75,98,59,81,66,43,69,85]

>>> sum =0.0

>>> n=0

>>> for x in L:

... if x<60:

... continue

... sum +=x

... n+=1

4.5 multi-loop nesting

>>> for x in [' A ', ' B ', ' C ']:

... for y in [' 1 ', ' 2 ', ' 3 ']:

... print X+y

Python Basics--04 Flow control statements