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some python grammar

admin 1月 28, 2021 0

1.Built-In Types and Data Structures

2.Control Flow

if Statements

if x < 0:
    print("x < 0")
elif x == 0:
    print("x==0")
else:
    print("x > 0")

for Statements

for w in words[:]:  
...     if len(w) > 6:
...         words.insert(0, w)
...
words
['defenestrate', 'cat', 'window', 'defenestrate']

range() Function

for i in range(3):
...     print(i)
...
0
1
2
list(range(5))
[0, 1, 2, 3, 4]

break and continue Statements, and else Clauses on Loops The else Clauses is executed when the loop terminates through exhaustion of the list (with for) or when the condition becomes false (with while), but not when the loop is terminated by a break statement.

for n in range(2, 5):
...     for x in range(2, n):
...         if n % x == 0:
...             print(n, 'equals', x, '*', n//x)
...             break
...     else:
...         # loop fell through without finding a factor
...         print(n, 'is a prime number')
...
2 is a prime number
3 is a prime number
4 equals 2 * 2

Defining Functions

>>> def (n):    # write Fibonacci series up to n
...     """Print a Fibonacci series up to n."""
...     a, b = 0, 1
...     while a < n:
...         print(a, end=' ')
...         a, b = b, a+b
...     print()
...
>>> # Now call the function we just defined:
... fib(2000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597
#---------------------------------------------------------
# parameter passing
def foo(a, b):
    "parameter passing in function"
    print(">>>parameter passing")
    print("addr(a) = {:#X}, addr(b) = {:#X}".format(id(a), id(b)))
    a = 2
    b.append(1)
    print(">>>assignments")
    print("addr(a) = {:#X}, addr(b) = {:#X}".format(id(a), id(b)))

c = 1
d = [12]
print(">>>before")
print("addr(c) = {:#X}, addr(d) = {:#X}".format(id(c), id(d)))
foo(c, d)
print(">>>after")
print("c = {0}, d = {1}".format(c, d))

>>>before
addr(c) = 0X560BA944AE80, addr(d) = 0X7F9D78C13108
>>>parameter passing
addr(a) = 0X560BA944AE80, addr(b) = 0X7F9D78C13108
>>>assignments
addr(a) = 0X560BA944AEA0, addr(b) = 0X7F9D78C13108
>>>after
c = 1, d = [12, 1]