itertools in Python (1)

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*Memo for itertools:

• My post explains cycle() and repeat().
• My post explains accumulate() and batched().
• My post explains chain(), chain.from_iterable() and compress().
• My post explains filterfalse(), takewhile() and dropwhile().
• My post explains groupby().
• My post explains islice() and pairwise().
• My post explains starmap(), tee() and zip_longest().
• My post explains product().
• My post explains permutations().
• My post explains combinations() and combinations_with_replacement().

*Memo for others:

• My post explains an iterator (1).

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itertools has the functions to create iterators.

*more-itertools has more functions by installing with pip install more-itertools.

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count() can return the iterator which endlessly generates a number one by one as shown below:

*Memo:

• The 1st argument is start(Optional-Default:0-Type:int/float/complex):
  • It's a start number.
• The 2nd argument is step(Optional-Default:1-Type:int/float/complex):
  • It's the interval of numbers.

from itertools import count

v = count()
v = count(start=0, step=1)

print(v)
# count(0)

print(type(v))
# <class 'itertools.count'>

print(next(v)) # 0
print(next(v)) # 1
print(next(v)) # 2
print(next(v)) # 3
print(next(v)) # 4

from itertools import count

v = count()

print(v) # count(0)
print(v) # count(0)

print(next(v)) # 0

print(v) # count(1)
print(v) # count(1)

print(next(v)) # 1
print(next(v)) # 2

print(v) # count(3)
print(v) # count(3)

print(next(v)) # 3
print(next(v)) # 4

print(v) # count(5)
print(v) # count(5)

from itertools import count

for x in count():
    if x == 5:
        break
    print(x)
# 0
# 1
# 2
# 3
# 4

from itertools import count

for x in count(start=-5, step=3):
    if x == 10:
        break
    print(x)
# -5
# -2
# 1
# 4
# 7

from itertools import count

for x in count(start=-5.0, step=3.0):
    if x == 10:
        break
    print(x)
# -5.0
# -2.0
# 1.0
# 4.0
# 7.0

from itertools import count

for x in count(start=-5.0+0.0j, step=3.0+0.0j):
    if x == 10:
        break
    print(x)
# (-5+0j)
# (-2+0j)
# (1+0j)
# (4+0j)
# (7+0j)

from itertools import count

for x in count(start=5, step=-3):
    if x == -10:
        break
    print(x)
# 5
# 2
# -1
# -4
# -7