withopen("welcome.txt","r")asfile:# 'file' refers directly to "welcome.txt"
data=file.read()# It closes the file automatically at the end of scope, no need for `file.close()`.
[File manipulation] Writing (append)
file=open("Hello.txt","a")# open in append mode
file.write("Hello World again")file.close()
[File manipulation] Writing (overwrite)
file=open("hello.txt","w")# open in write mode 'w'
file.write("Hello World")text_lines=["First line","Second line","Last line"]file.writelines(text_lines)file.close()
[File manipulation] Reading
file=open("hello.txt","r")# open in read mode 'r'
file.close()
print(file.read())# read the entire file and set the cursor at the end of file
printfile.readline()# Reading one line
file.seek(0,0)# place the cursor at the beggining of the file
[fn(i) for i in list] # .map
map(fn, list) # .map, returns iterator
filter(fn, list) # .filter, returns iterator
[fn(i) for i in list if i > 0] # .filter.map
str[0:4]
len(str)
string.replace("-", " ")
",".join(list)
"hi {0}".format('j')
f"hi {name}" # same as "hi {}".format('name')
str.find(",")
str.index(",") # same, but raises IndexError
str.count(",")
str.split(",")
str.lower()
str.upper()
str.title()
str.lstrip()
str.rstrip()
str.strip()
str.islower()
/* escape characters */
>>> 'doesn\'t' # use \' to escape the single quote...
"doesn't"
>>> "doesn't" # ...or use double quotes instead
"doesn't"
>>> '"Yes," they said.'
'"Yes," they said.'
>>> "\"Yes,\" they said."
'"Yes," they said.'
>>> '"Isn\'t," they said.'
'"Isn\'t," they said.'
Iteration
for item in ["a", "b", "c"]:
for i in range(4): # 0 to 3
for i in range(4, 8): # 4 to 7
for i in range(1, 9, 2): # 1, 3, 5, 7
for key, val in dict.items():
for index, item in enumerate(list):
Dict
dict.keys()
dict.values()
"key" in dict # let's say this returns False, then...
dict["key"] # ...this raises KeyError
dict.get("key") # ...this returns None
dict.setdefault("key", 1)
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