# Print & Open

> Markdown source of <https://docs.calebsargeant.com/programming/python/other/print-open/>.

## For Loops

<https://www.kite.com/python/answers/how-to-iterate-through-the-lines-of-a-file-in-python#>:~:text=Use%20a%20for%2Dloop%20to,line%20break%20from%20each%20line.

``` python
with open("sample.txt", "r") as a_file:
for line in a_file:
  stripped_line = line.strip()
  print(stripped_line)
```

## If Statements

<https://stackabuse.com/python-check-if-string-contains-substring/>

``` python
substring = "caleb"
fullstring = "calebsargeant"

if substring in fullstring:
    print("fullstring contains substring")
else:
    print("fullstring does not contain substring")
```

<https://www.w3schools.com/python/python_conditions.asp>

``` python
a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")
```

<https://stackoverflow.com/questions/5899497/how-can-i-check-the-extension-of-a-file>

``` python
if file.endswith('.docx'):
  print("it's a document")
elif file.endswith('.xlsx'):
  print("it's a spreadsheet")
else:
  print("whatever")
```

## Redirect Output to File

<https://stackoverflow.com/questions/7152762/how-to-redirect-print-output-to-a-file-using-python>

<https://stackoverflow.com/questions/36571560/directing-print-output-to-a-txt-file>

Using open to output to file. `a` appends and `w` writes.

``` python
# print into a file
with open(filename, "a") as f:
  print(myvar.strip(), file=open(f), "a")

# Similarly, showing py2 vs py3
with open('output.txt', 'w') as f:
  print >> f, 'Filename:', filename     # Python 2.x
  print('Filename:', filename, file=f)  # Python 3.x
```

Redirecting `stdout` to file, but printing directly to file is better:

``` python
import sys

orig_stdout = sys.stdout
f = open('out.txt', 'w')
sys.stdout = f

for i in range(2):
  print 'i = ', i

sys.stdout = orig_stdout
f.close()
```

## Searching a File

<https://www.kite.com/python/answers/how-to-search-a-file-using-grep-in-python>

``` python
file = open("grep_sample.txt", "w")

file.write("first line\nsecond line\nthird line")
file.close()

pattern = "second"

file = open("grep_sample.txt", "r")
for line in file:
    if re.search(pattern, line):
        print(line)
```

## CSV Files

It's easier to just iterate a file using `csv.reader` without going `for row in reader` and `for column in row`.

<https://stackoverflow.com/questions/49266463/read-csv-file-in-python-and-iterate-each-line-item-as-a-value-in-a-script/49266632>

``` python
# Iterate over flat-file list OR a single column CSV file, header row cannot exist, or will be included as value to iterate over.
with open(foodlist, 'r') as food:
  for (veg,) in csv.reader(food, delimiter=','):
    veg = veg.strip()
    print(veg)

# Iterate over a CSV file with more than one column, specifying header row values:
with open(foodlist, 'r') as food:
  for (veg, fruit, protein) in csv.reader(food, delimiter=','):
    veg = veg.strip()
    print(veg)

# Iterate over a CSV file with more than one column, not caring about other header row values:
with open(foodlist, 'r') as food:
  for (veg, _, _) in csv.reader(food, delimiter=','):
    veg = veg.strip()
    print(veg)
```

<https://www.programiz.com/python-programming/reading-csv-files>

``` python
import csv
with open('my.csv', 'r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)
```

<https://stackoverflow.com/questions/45947887/python-looping-through-csv-files-and-their-columns>

``` python
for i in numFiles:
  file = open(os.path.join(pathName, i), "rU")
  reader = csv.reader(file, delimiter=',')
  for row in reader:
      for column in row:
          print(column)
          if column=="SPECIFIC VALUE":
              #do stuff
```

## Content-Type of Files

<https://stackoverflow.com/questions/20244757/content-type-in-for-individual-files-in-python-requests>

``` python
files = {
  'doc': ('example.docx', open('/Path/to/example.docx', 'rb'), 'application/vnd.openxmlformats-officedocument.wordprocessingml.document')
  }
```