Coursera_ Python for Genomic Data 笔记001
range( )：
If you do need to iterate over a sequence of numbers, the built-in function range( ) comes in handy. It generates arithmetic progressions（等差数列）
range(1,5) -> [1,2,3,4] dosen't including 5
range(1,5,2) -> [1,3] step by 2
range(5) -> [0,1,2,3,4] from 0 to 5 and doesn't including 5
array[ ]:
[1,2,3,4,5]
0, 1, 2, 3, 4 "No." start from 0
-5, -4, -3, -2 ,-1 "reverse No." start from 1
array[0:]
array[1:]
array[:-1]
array[3,-3]
x = [:] make a new arry
array[::2] step by 2 start from the first element(No.0)
array[2::] start from the third element(No.2) step by 2
x.reverse( )
array[::-1] step by 1 start from the last element(No.-1)
array[::-2] step by 2 start from the last element(No.-1)
来自coursera python 课程里面的def：
def has_stop_codon(dna):
"this function check if given dna seq has in frame stop codons."
stop_codon_found=False
stop_codons=['tga','tag','taa']
for i in range(0,len(dna),3):
# start from the first element(No.0) to the last element, step by 3
codon=dna[i:i+3].lower()
if codon in stop_codons:
stop_codon_found=True
break
return stop_codon_found
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