Note 2 - body and structure

标签（空格分隔）： python

Learning techniques

Assuming you are playing << call of duty >> and need go through one difficult scene where has many options and the duplicate operations like pulling trigger.

1.Condition statement

1.1 Definition

#syntax
#boolean expression :a cimbination of comparsion operators and logic operators
if boolean expression :
elif boolean expression :
else :

Example:

# if 
age = 20
if age < 18 :
    print("youngster")
elif age == 18 :
    print("18")
else:
    print("adult")

1.2 deeper intuition

If statement exactly follows the sementic rules as if these statements looks like a short story!

if bool(true)->keep going
bool(false)->else / elif(iteration)

Extra point: input()

a = input("please input your age!")

The terminal prompts you to input age-> that means you need to type your age on the console.

1.3 nested if statement

Inner one if statement is nested into the outer if statement

if boolean expression :
    if boolean expression :
    #....

2. loop statement

1. while
2. for

keywords:

1. continue
2. break
3. else
4. pass

2.1 while

Example:

i = 1
while i <= 10 :
    print("still in loop body",i)
    i += 1
    if i == 10 :
        break

else :
    print("jump out of loop then execute else")

We can single out some important points:

1.syntax

while boolean-expression :
    loop body
    continue # stop this sub-course and jump directly to next sub-course
    break # terminate the whole loop and execute the next statement
else:
##else executed if the entire lopp is executed but jump over to the underneath statement if loop ##body executes break

2.2 for

Example:

for element in collection :
    continue # same as while 
    break # same as while
else:
    # same as while when break within loop body is executed makes else block cannot be executed 

When I first learned to program with python in the way as I do in Java,especially retrieving the entire list in python.I hardly got used to code for statement in python.But a suggestion is given for this problem.

for i in range(10)[
# equivalent to ->
# for (int i = 0 ; i < a.length ; i++ )

^[1]

2.3 pass

As result of facilitating the complement for code in the future,we can use keyword pass to occupy some space to be available later.

3.iterator and generator

what we learn here is just getting our feet wet.

3.1 Iterator

Iterator is for retrieving the whole element in a collection like list and so forth.
There are two crucial functions of it: iter() [exclusive]and next()[general]

a = [1,2,3,4,5,6,7,8,9,10]

iterator = iter(a)

while True :
    print(next(iterator),end=",")

The terminal shows:

1,2,3,4,5,6,7,8,9,10,Traceback (most recent call last):
  File "d:\workspace\python\learning_06.py", line 6, in <module>
    print(next(iterator),end=",")
StopIteration

3.2 generator

pass block