Python Learning notes Conditional loops and other statements

Assignment statements

Normal Assignment:

>>> x, y, z =
>>> print x, Y, Z
1 2 3
>>> x, y = y,x
>>> print x, y
2 1

Tuple (Sequence) unpack assignment:

>>> a = (a)
>>> x, y, z = a
>>> x
1

Dictionary assignment:

>>> people = {"Name": "CQ", "Age": "20"}
>>> Key,value = People.popitem ()
>>> Key
' Age '
>>> value
' 20 '

Increment Assignment:

>>> x = 5
>>> x + = 2 #x = x + 2

>>> x
7
>>> x *= 3 #x = x * 3
>>> x
21st

Conditional statements:

Remembering statement blocks

If something:

Do

Elif anothing:

Do

Else

Do

Understand the following Boolean operator, the basic ture,false

While loop: (just give a condition, but keep running the program when it meets the criteria)

>>> x = 1
>>> while x < 10:
... print X
... x + = 1
...
1
2
3
4
5
6
7
8
9

For loop: (Gives a range, loops within the range)

>>> for x in range (10):
... print X
...
0
1
2
3
4
5
6
7
8
9

If you can use a for loop, try not to use a while loop (while easily causing a dead loop)

Jump out of the loop:

Break

>>> for I in Range (99,0,-1):
... if i%2 = = 0:
... print I
... break
...
98 #从99 to 0 steps to 1, the first to meet the conditions to jump out of the loop, and not to print all, if there is no break will print all

While True/break

>>> while True:
... word = raw_input (' Enter a word: ')
... if not word:
... break
.. else:
The. print ' the word is ' + word #当输入一个值时, will print the value and continue the loop request Enter a If Word does not enter, then jump out of the loop

List Deduction---Light-weight loops:

>>> [x * x for x in range (10)]
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
>>> [x * x for x in range] if x%2 = = 0]
[0, 4, 16, 36, 64]

Python Learning notes Conditional loops and other statements