[Notes] Learn Python2.7 From Python Tutorial

• I have planed to learn Python for many times.
• I have started to learn Python for many times .
• However, I can't use it fluently up to now.
• Now I know I was wrong.
• I just tried to remember the syntax and took notes on paper with little practice.
• Now I print the Python Tutorial and learn it by using it.
• Practice. Practice. Practice.
• I love Python. It is glamourous.

Here are notes:

# In interactive mode, the last printed expression is assigned to the variable _
>>> price * tax
7.5
>>> price + _
113.0625

---

# use raw string
>>> print 'C:\some\name'
C:\some
ame
>>> print r'C:\some\name'
C:\some\name

---

# use triple-quotes:
>>> print """\  #  \ is to prevent  \n
Usage: thingy [OPTIONS]
    -h
    -H hostname
"""

---

>>> 3 * ('pyth' 'on')
'pythonpythonpython'

---

# slice
>>> word = 'Python'
>>> word[ :2]
'Pyt'
>>> word[0] = 'J' # error. You can't do this.
>>> len(word)
6

---

# use Unicode strings.
>>> u'Hello\u0020World!'
u'Hello World'
>>> ur'Hello\\u0020world'
>>> u'Hello\\\\u0020world'

---

# list
>>> squares = [1, 'abc', 9, 16, 25]
>>> squares[1][1]
'b'
>>> squares.append("abcd")
>>> a = ['a', 'b', 'c']
>>> n = [1, 2, 3]
>>> x = [a, n]

---

# Fibonacci series:
while b < 10:
     print b
     a, b = b, a+b

---

# Control Flow
# if
if x < 0:
    x = 0
elif x == 0:
    x = 1
else:
    print 'Ok'

# for - 1
words = ['cat', 'window', 'defenestrate']
for w in words:
    print w, len(w)

# for - 2
for w in words[:]:
    if len(w) > 6:
        words.insert(0, w)
# here is a question: I use 'for w in words' while that can't make sense. Why?

---

>>> range(0, 10, 3)
[0, 3, 6, 9]

a = ['a', 'b', 'c']
for i in range(len(a)):
    print i, a[i]

# you can alse use:
for index, item in enumerate(a):
    print index, item

---

# break & continue & else on LOOP:
for n in  range(2, 10):
    for x in range(2, n):
        if n % x == 0:
            print n, 'equals', x, '*', n/x
            break
    # The else belongs to the 'for' loop, not the 'if' statement.
    else:
        # loop fell through without finding a factor
        print n, 'is a prime number'