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Idiomatic loops¶

Looping in general¶

In [1]:

data=["John","Doe","was","here"]

In [2]:

idx=0whileidx<len(data):print(data[idx])idx+=1

JohnDoewashere

In [3]:

foridxinrange(len(data)):print(data[idx])

JohnDoewashere

¶

In [4]:

foritemindata:print(item)

JohnDoewashere

In [5]:

foridx,valinenumerate(data):print(f"{idx}:{val}")

0: John1: Doe2: was3: here

Looping over a range of numbers¶

In [6]:

i=0whilei<6:print(i)i+=1

In [7]:

forvalin[0,1,2,3,4,5]:print(val)

¶

In [8]:

forvalinrange(6):print(val)

Reversed looping¶

In [9]:

data=["first","to","last","from"]

In [10]:

i=len(data)-1whilei>=0:print(data[i])i-=1

fromlasttofirst

¶

In [11]:

foriteminreversed(data):print(item)

fromlasttofirst

Looping overn collections simultaneously¶

In [12]:

collection1=["a","b","c"]collection2=(10,20,30,40,50)collection3=["John","Doe",True]

In [13]:

shortest=len(collection1)iflen(collection2)<shortest:shortest=len(collection2)iflen(collection3)<shortest:shortest=len(collection3)i=0whilei<shortest:print(collection1[i],collection2[i],collection3[i])i+=1

a 10 Johnb 20 Doec 30 True

In [14]:

shortest=min(len(collection1),len(collection2),len(collection3))foriinrange(shortest):print(collection1[i],collection2[i],collection3[i])

a 10 Johnb 20 Doec 30 True

¶

In [15]:

forfirst,second,thirdinzip(collection1,collection2,collection3):print(first,second,third)

a 10 Johnb 20 Doec 30 True

In [16]:

my_dict=dict(zip(collection1,collection2))print(my_dict)

{'a': 10, 'b': 20, 'c': 30}

`for - else` - Checking for a match in a collection¶

Let's say we want to verify a certain condition is met by at least one element in a collection. Let's consider the following relatively naive example where we want to verify that at least one item is "python" (case insensitive) indata. If not, we'll raise a ValueError.

In [17]:

data=[1,2,3,"This","is","just","a","random","Python","list"]

In [18]:

found=Falseforvalindata:ifstr(val).lower()=="python":found=Truebreakifnotfound:raiseValueError("Nope, couldn't find.")

¶

In [19]:

forvalindata:ifstr(val).lower()=="python":breakelse:raiseValueError("Nope, couldn't find.")

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